Hi
You not loosing your mind as it is not there :)
That is what is called a flow field in NAV, it is an always up to date field containing the totals from a sub table, these totals are stored in the tables at the top of the list in SQL with the numbers in the table name (For this reason you should never update records in SQL for a NAV system or all sorts of things break)
The number in the table name is actually the table number that it is holding these sums for so if you look for 32, then for the key of the record from NAV you will see the set of field totals
I haven't looked at it in a while as the way that works changes in NAV 2009 and up but if you look at the record in NAV then compare the numbers to that table you can figure out how it fits together,
My suggestion though, don't use that table, rather see how NAV calculates that amount and just add it up yourself in your SQL Query, in the long run it will give you less grey hairs
Hope this helps
Nev