He offset the advantage of the belt of strength. IE, he made him back to twice as strong as Thor. IE 4 times as strong as normal Thor. Why would he offset the strength to just above Thor when he was immensely pleased with what 2x Thor Kurse was doing?
Though it is interesting, and I guess I never looked into it, but I figured that the statement would be there in spades.
Curious if it was ever literally stated, because anyone not named Superman needs a literal statement to be right.