Problems with sizing in Mood Pattern

Hey guys, I'm a beginner sewist and I'm trying to make some clothes for myself to practice. I printed the lavender t-shirt from Mood to learn how to read a pattern and everything.

But one thing is getting me really confuse: the sizing. Where I'm from (S, M, L), we use a different sizing chart and centimeters. With the table that they have, I'm a 14 but when comparing to my normal t-shirt thats too big.

Can someone help me figuring out this part? I'm a Medium