What "Record Number" are you storing? I hope it isn't the one at the bottom of the form which isn in the navigation controls which say Record X of Y. That has nothing to do with the actual record that is in that form. It is just an arbitrary numbering of the current recordset.
Access doesn't store data in the tables in any meaningful order. And when you open a form with a table as the recordset, there is no guarantee that record 5 will be the same record when you open the form again. That numbering is ONLY good for the current session of the form. The minute it is closed or requeried, you can throw that number out the window. Now, it may SEEM like the numbers are the same as many times the data does come into the form in the same order, but unless you apply an Order By in a query and use that as the underlying recordsource of the form, the records will not be in any particular order. And if records are added or deleted it is possible to have them mix up even more.