A knitting pattern question

[Nousernameforme]

Im quite new to knitting and im working on this sleeve. I read it as increase 1 stirch either end of the row every 4 rows. Im making the biggest size so I would need to increase 50 stitches so if my maths is right that would be 200 rows which seems like it would be massive. It's in Aran if that makes a difference I've increased up to 63 stitches so far and its already measuring half way up the forearm. Am I following the instructions correctly? Is the pattern incorrect or should I just trust the process.
Also its a free pattern so im not posting anyone's paid content.

Your maths is wrong; inc 2 stitches every 4 rows is like 1 stitch every 2 rows so to get to 50 that would be 100 not 200.
If it’s already looking too big, have you been doing the right number of increases?

100 sounds a lot more reasonable ill keep going and if it turns out massive ill cross that bridge when it comes to it

Before you go further. Are you using the yarn specified in the pattern and the same size needles?
When you did your tension square did you use double the number of stitches and rows then wash, block and dry before measuring number of stitches and rows. The number you knit needs to be the same as specified for the tension given in the pattern and also match that on the band from the yarn. If your tension is wrong you need to get it right or the garment will not be the correct size and sleeves and neck will likely be too slack or too tight. A lot of new knitters don’t do the tension square but you do need to.
From the tension square you will know exactly how many inches (or cm) the sleeve will be after the 100 increase rows.

I have just checked some of my patterns. For Aran 100 rows will be 16.5 inches. Is that the measurement given on the size diagram for the point on the sleeve where that increase is? It sounds like you might be using a double knit not Aran pattern

For the smallest size you have to increase from 43 to 73 which equals 30 in total.

A stitch at both ends, so there will be 15 rows where you increase, every 4 rows. 15 x 4 = 60 rows