Hi!,
Like you, I use the Number field because, as you see, it is not a unique field. The overall unique field is the CMDNUMWK which is not visible on the window. Another field, the RecNumControl field, is unique to each checkbook ID. This field is likewise not visible on the window.
The benefits on the research side is that the 'Number' turns into the Originating Document Number in the GL. The Description on the Bank Trx entry window turns into the Reference on the Journal entry. Just be aware (as you most likely are) that the Paid To/ Recd From field is not written over to the GL.
Kind regards,
Leslie