Easy Saturday Cardigan (sleeve instructions)

This is very confusing! Pattern reads "Change to larger needles and proceed in stocking st., increase 1 st. each end of 3rd and every following 4th row until there are 37 sts., then every following 6th row from previous inc. until there are 49 sts.
Don’t understand - what and how many rows are we supposed to be doing to make up the pattern for the sleeves? Do we just knit 1, purl 1, and count upwards from there? If so, how do we end up having more than one 6th row? Confusing. Tried to find a video tutorial online - there is one, but she totally skips this part, so no help at all.

Welcome to KnittingHelp!
These instructions can be confusing but they’re quite common when describing inc/dec in shaping sweater parts.
Increase at each end of row 3 and then rows 7,11,15,19, etc. until you get to 37sts.
You get to 37sts on row 19, then you increase at each end on rows 25, 31,37,43, etc until you get to 49sts.

Thank you so much for your help SalmonMac. Much clearer to me now. I was getting caught up not knowing if it meant to do every 3rd & 4th row, but you have now explained it very well and I can continue. Appreciate your help very much. Have a good day.