Sounds like a possible alignment issue. When loading the forms into the printer, how many checks are needed to load into tractor feed before the first printed one? some time it’s 2 or 3 depending on the check stock. So when you do a check run and it asks for starting check number you need to add this “extra”. For example loading forms into printer check numbers 200,201,202 are needed to load the tractor feed. The first printable check number would be 203. Check numbers 200,201 and 202 become waste and should be voided.