Determination of conservative residues via Conservation Code

Question

[shilyaev.n.g]

Good day.

I search conservative residues of protein and try to work with Conservation Code. Output of CC give 2 columns (position of residues and their score), but don't clearly understand how use this. Which threshold value will optimal for confident assignment residues as conservative?

http://compbio.cs.princeton.edu/conservation/

Thx.