Need help with sweater sleeve

I am working on a striped baby sweater. The directions for the sleeves confuse me. They read “increase 1 st at each end of the 3rd row and every foll 4th row until there are 54 sts” (I have 34 sts on the needle right now).

Does that mean on each 3rd and 4th row increase a stitch at each end? Or does that mean on my first 3rd row and then only on each following 4th row? If I increase the stitches the first way, I will increase it much quicker than the second way. I was thinking of just biting the bullet and trying one way and then pulling it out if it looks wrong.

Any suggestions are much appreciated!

Increase on the 3rd, then every following 4th row. So you’d increase on 3, 7, 11, 15, etc.