What’s the deal with the ending of Mark, and where do you think the ending actually is? Is after verse 8 or 20 in Chapter 16? And what would the reason be that there is a discrepancy where the end of the book is? It just doesn't seem the appropriate place to not be too sure. I guess I would think that with something as important as the bible, there would not be anything that would leave room for "personal interpretation" or "guessing."

There is a short and a long answer to your question; I will try to land somewhere in the middle.

Most of the complaints about the verses in Mark 16:9-20 start in the 19th century because the critics believe that Mark should stop after 16:8. The added verses are NOT arbitrary and are not added simply because someone felt like it. Many of our current manuscripts from Mark contain the ending you have in your bible but the style is a bit different from the rest of Mark (which some suggest makes the ending not part of the original).

From the oldest manuscripts we have found, (“we” meaning the church as whole and biblical scholars specifically) the last twelve verses are missing.  There are even a handful of manuscripts that include a shorter ending before the current longer one in your bible today (this exists in the oldest Latin Codex in existence).

What you have to understand is that the current ending of Mark is consistent with the gospel accounts, there is nothing out of place with it. What the note tries to give you is simple honesty: SOME (not all) early manuscripts have it missing. This could be scribal error, the addition could be tacked on because a scribe somewhere didn't like the abrupt ending, or the original ending could have been lost (which is not uncommon with ancient scrolls due to their wearing patterns), or the gospel may have been unfinished, due to death or some form of persecution.

There is also evidence that it was part of the original though. Justin Martyr (one of the original church fathers) wrote a famous work called the Apology (Defense of the Gospel) in AD 160; he states that Ps. 110:2 was fulfilled when Jesus' disciples, going forth from Jerusalem, preached everywhere. His wording is remarkably similar to the wording of Mk. 16:20. Justin's student Tatian (AD 172) incorporated the "Longer Ending" into his Diatessaron (this was a blended narrative consisting of material from all four canonical Gospels – I have a copy you can read if you want). Irenaeus (in AD 180) quoted from the verses 9-20 specifically as part of Mark's gospel.

Critics are divided over whether the original ending at 16:8 was intentional, or whether it resulted from accidental loss, or even the author's death.

To give you more food for thought (and not meant to confuse you at all), in some of our earliest manuscripts there is a shorter ending, which is then followed by the current ending. These appear together in 6 Greek manuscripts, and in dozens of Ethiopic copies. I know you are wondering “what does the shorter ending say,” because I know you want to know, this is it (with slight variations): “But they reported briefly to Peter and those with him all that they had been told. And after this, Jesus himself sent out by means of them, from east to west, the sacred and imperishable proclamation of eternal salvation."

There is huge disagreement among scholars as to whether Mark originally stopped writing at 16:8 -- and if he did so, if it was deliberate or not—or if he continued writing an ending which is now lost. Allusions to a future meeting in Galilee between Jesus and the disciples (in Mark 14:28 and 16:7) seem to suggest that whether what we have the real ending or not, Mark intended to write beyond 16:8.

Some interpreters have concluded that Mark's intended readers already knew the traditions of Jesus' appearances, and that Mark brings the story to a close at 16:8 to highlight the resurrection and leave anticipation of His return.

Either way, whether it belongs or not, nothing about it is arbitrary. It has been thoroughly thought out, researched, and placed in scripture. They give you the footnote for honesty’s sake. It is their way of letting you know what we have and what we don’t, so you as the reader have nothing hidden from and are fully infirmed.

And whichever way you see it, it is all good news, the tomb is empty and He is risen.