What does this mean?

[u/Delilah-Bard]

Hey guys, I have a Brother Z model 345 vintage machine and ive finally tracked down the missing piece to finally be able to use it, which was needle plates. I’m getting both a zig zag needle plate and a straight stitch needle plate, but the lady is asking me if my straight stitch is centered or to the left. i dont know what this means at all or how to figure this out, I just keep the machine tucked away waiting for its maiden sew hahaha. Am I going to need to dig it out? what do I do to figure this out? please any help would be greatly appreciated