How to select T-Shirt size?

Hey Trrailblazers!

I got a mail from Trailhead that says I won a TrailheaDX Shirt.

Now the problem is while redeeming the prize, I'm a bit confused about how to select its size cuz I wear Tees which is mostly 40+ (in size) whereas here I'm getting to see only these size numbers.

Can anyone help me out with this?

#Trailhead #Trailhead Challenges #TrailblazerCommunity #Trailblazers #TrailheaDX2021 #TrailblazerCommunityHelp