To Increase stitches on sleeves

Hi
I am a bit confused with the following instruction. Do I increase 1 st at each end on EVERY 9th and 18th row OR just on 9th row, then 18th row, then every 18th row?

“Cont in patt, shaping sides by inc 1 st at each end of 9th [7th: 7th: 5th] and every foll 18th [16th: 14th: 12th] row to 83 [87: 87: 85] sts”
Thanks in advance

thank you

Increase at each end on row 9 and then on every following 18th which is 27, 45, 63, 81 and so on til you reach 83 sts. That’s 2 sts increased per increase row.