Catcher rating

I am confused about how to read the catcher card. Does T-20 mean that whenever there is a throwing error chance it will be an error, or does it mean there is a 1 in 20 chance that there will be a throwing error. The catcher is listed as e2.

Thank you.

Whenever there is a stolen base attempt the twenty sider is rolled to determine if the basestealer is successful. After computing the hold and catcher arm ratings as an example the basestealer would be safe on a roll of 1-14 and out 15-20. If the result is a 1,2 or 3 then another roll has to be made to see if the catcher threw the ball into cf as an error advancing the basestealer to third. A catcher's T rating is what is used. If the catcher has a T rating of 5 then 1-5 is a throwing error on the play and 6-20 is no throwing error. In your example, every successful stolen base with a result of 1,2 or 3 will be an automatic throwing error on the catcher.