T-shirts are a baggy fit and are not fitted. 

When you receive your shirt- 

A size small is marked as M (approx size 6-8) 

A size medium is marked as L (approx size 8-10) 

A size large is marked as XL (approx size 12-14) 

Please be aware you have not received the wrong size shirt this is just our sizing system due to our new supplier.