Hi jc,
Good question. We want you to understand our notations, as we think they are very helpful!  
 
 
FL - 
Flaw in the Reasoning question type
#% - Stimulus contains numbers & percentages
CE - Stimulus contains 
Cause and 
Effect reasoning
PR - 
Principle questions (not a separate question type, but an "overlay" that appears in other question types, for example Strengthen - PR)
FIB - 
Fill in the 
Blank (also not a separate question type, but the question stem asks you to fill in the blank in the stimulus)