Garment sizing

[Frayed knot]

Hi there 

I’m a newbie to the site and crochet. I managed to make a arigurumi llama from a pattern so feel confident to make a waistcoat for my mum but got confused when it had repeated numbers in parentheses (3,3,3,4,4,5) I do need to size up but what do those numbers mean? 
it says choose the number you need and circles them in the pattern but why are they repeated? Pattern uploaded
TIA

frayed knot. 

[Granny Square]

This pattern has multiple sizes, it is so teeny even on my big monitor I can hardly read it , but I think it's 7 sizes: XS(S, M, L, 1x, 2x, 3x)

After that there is a note that says something like 'pattern is written for extra small, other sizes in parentheses), this is not uncommon for garments.

How this works is first you need to figure out what size to make, let's say your mom is a Large, which is the 3rd number within the parentheses.  What I do when I'm making a pattern like this is (first I print it out because I hate working from a device), then second I go thru the whole pattern and everywhere there is the multiple size notation I circle my size so I don't use the wrong number by mistake.  So your case go thru the whole pattern carefully and every time you see  a string of 1 number followed by 6 numbers in parentheses, and circle or highlight the number you need to follow for the size you are making. 

An example of a notation might be something like "DC in the next 1(2,3,4,5,6,7) stitches, increase in the next stitch" for example, and you can see I've bolded the large size.

[Frayed knot]

Thank you Granny Square. Sorry the pattern is small. I thought it would zoom in but it is a bit blurry. 
I think I understand. 
you explain things very well. 
blessings