There are some different approaches to achieve what you desire, if I understood you correctly.
One simple way I can think of is the following:
In AttrCalculate.lua, locate the function "ExAttrCheck(role)" .
After the local variables declarations, add the following:
if job == JOB_TYPE_SHENGZHIZHE or job == JOB_TYPE_HANGHAISHI or job == JOB_TYPE_FENGYINSHI then
mnatk = mnatk + (Sta(role) * 1 + math.pow(math.floor( Sta(role)*4/20), 2 )) -- Or whatever formula you want to use for minimum attack
mxatk = mxatk + (Sta(role) * 1 + math.pow(math.floor( Sta(role)*4/20), 2 )) -- Or whatever formula you want to use for maximum attack
end
I haven't tested it tho.