I'll second Toolguy's suggestion of tightening one side reasonably snug and then moving the other. If both sides are loose there are just too many ways the thing can squirm. Is it pivoting around some point? Is that point near the middle or not? Is it sliding so both sides are moving across the table? With one side snug(er) you're more nearly assured about the kind of movement. Since the pivot is way off the end, you'll need to move more than the amount indicated. That is, supposing the right end is .010" too close to you. You tap it back .010", but since the pivot is further left than the left end of the vise jaw, the left end might move .002" as the right moves .010" so you have to compensate for that.
I do deviate from Toolguy in not switching sides and loosening the snug side since it can move inadvertently. Maybe it's just a matter of style or preference or superstition.
"In theory there’s no difference between theory and practice. In practice there’s a lot of difference.” Yogi Berra