Autofill does not recognize pattern: 1000-1, 1001-1, 1002-1...

Hello,

I need some help customizing my worksheet to autofill the numbers listed above. Instead of following the pattern of 1000-1, 1001-1, 1002-1, Excel is autofilling as 1000-2, 1001-2, 1002-2... Is there a way to change this formatting?

Here's what I actually have in the cells:

FLAIR
MODEL SN-580-24-AB
Serial Number: XO1000-1

I need to change each serial number to XO1001-1, XO1002-1...

Thanks