TN "TARGET NUMBER"

A target number (Commonlly referred to as a TN) is the number you are 
rolling your dice against in a specific test. Shadowrun is a D6 system 
so numbers are generally in single digits. A standard TN for a test 
is 4. If any dice are rolled equal to or higher than the TN it is 
classed as a success, though any roll  of 1 is counted as an automatic 
failure, no matter what the TN is.

For TNs higher than 6 you must first roll a 6, then another number
that when added to 6 would be greater than the TN to score a success.