the LAST stitch in any row was previously the First stitch in the row.
as you progress, make a habit of making the first stitch (or two) snug..
as you 'work' a row, you move ease from stitch to stitch (think of a ball park WAVE--the ease moves from stitch to stitch.
when it come to last stitch.. it gets stuck!
so the last stitch 'catches' all the ease of the row..
and this can make it loose and sloppy looking.
but if ,on previous row, you made the first (now the last) stitch snug. .it can absorb the extra ease with out becoming too big..
UNFORTUNATELY--its hard to do with the cast on row!
so you will have 1 row with 1 oversized stitch.
you can twist it to take up some of the ease..