[plt-scheme] Type Explanation

Hi,

I was trying to check the predicate for type Integer and tested integer?. I got:
> integer?
- : (Any -> Boolean : ((restrict Number)) ((remove Integer)))

What's the meaning of  ": ((restrict Number)) ((remove Integer)))"

Are these possibilities documented?

Cheers,

-- 
Paulo Jorge Matos - pocmatos at gmail.com
Webpage: http://www.personal.soton.ac.uk/pocm