I need help counting rows, please

I got interrupted by a phone call and now I can’t figure out how many rows I have completed. This is just a garter st. (straight knitting) but I am using a lot smaller needle than I am used to, my first time on 4’s, and between the size and the pattern I suddenly can’t figure out how many rows I have knit. How do you count them - I should know, but i keep getting different numbers so I am counting something wrong.

Count the bumps (purls) on one side and multiply by 2.