Can you share the part?
I suspect it is because of a pattern that you have created.
I think this has happened to me before. If you select one of the holes that is part of the pattern, it only shows the number that were patterned not including the original hole.
However, if you put the hole callout on the original hole, the number should update to the correct number.
I know that this is bad functionality, and may be a bug, but that was the way I fixed the problem.
OK, I see the issue.
The problem resides with the fact that the first slot that you created was a "thru all" slot. Essentially creating 2 holes on either side of the part. The hole callout only sees that one slot as a single item even though it created 2 holes.
If you delete the hole pattern and go back to the hole callout in the drawing, it only calls out 1 slot, even though there are 2 there.
Then you patterned it, and I would have expected the hole callout to only show a "3x". But for some reason, it is "counting" the number of instances that the geometric shape is shown, not including the original one, then adding 1.
So, I tried modifying it.
I created the first slot, but instead of going "thru all", I used "up to next". Then mirrored it to put it on the other side, then patterned both the slot and mirror.
When I brought it into a drawing and used the hole callout, I STILL got "5x" as the number on the hole callout. It was counting everything except the mirror. EVEN WHEN I PUT THE HOLE CALLOUT ON THE MIRRORED SLOT!
I don't know of a better way to do this other than to manually change the quantity to 6.
This might officially be a bug.