Different UOH frames on block!? why?

ive been wondering allot about UOH setups lately. i went and checked the frame data here: http://ensabahnur.free.fr/Baston/index.php?page=gameMoves&gameNum=20&charNum=3&charName=Chun-Li&gameName=Street%20Fighter%20III%20Third%20Strike

it says that chun’s UOH on block is "-5 ~ +7"
does anyone know the variable for this?

How late into the animation it hits.

Yep pretty much.

Distance/timing changes the frame advantage/disadvantage.