Help understanding this pattern!

the pattern is Ann Norling Adult Basic Sock! Im working on starting the heel. I divided the stitches and now the pattern says:

row 1 (right side) : Sl1, K1
row 2: Sl1, P rem sts across. Work 20 rows.
You will have half the # of slipped sts making it easy to count.
End after last sl1, K1 row.

after row 2 it says work 20 do i just do row 1 once and then do 20 of the row 2 or do i the go back to row 1 and then row 2 and keep doing that until i reach 20 rows. The reason why I am confused is because at the end it says…end after last sl1, K1 row which makes me think i have to repeat! help please I dont want to do 20 rows wrong and have to take it out!

Alternate rows 1 and 2 for 20 rows. It creates a sturdier heel stitch than a plain knit.