This is a little complicated.
There are three types of blocks:
A. Ok blocks. Have white motion vectors.
B. Blocks discarded due to bad motion vectors. Have red vectors.
C. Blocks discarded due to bad match. Have no motion vectors.
Which percentage do you want to see? The deep analysis kick-in percentage is compared to the ratio B / (A + B) and the frame discard limit is compared to the ratio A / (A + B + C). I think it makes sense to do that but it's somewhat confusing I guess, especially since it's not documented.