Hello and thank you for helping. My pattern says the following:
Cast on 12 stitches
Work 24 rows garter st (knit every row - first row is wrong side).
My question is probably silly, but is the row that you cast on counted as 'the first row' and one of the 24?
No, you don't count the cast on row as one of your knitted rows. So in this instance, you cast on and then you knit 24 rows.
With garter stitch each bumpy line on the fabric is two rows, so when you have done your twenty four rows you should have 12 'bumpy lines' under your knitting needle.
BTW it is only the questions that you don't ask that are silly.
If you ask, you have the opportunity to learn something new or to solve a problem. If you don't ask then there is no learning and you still have a problem!