Why is it written 32 bit and not 64?

I bought sketchup 64bits but when I go to the revo uninstaller I saw it was 32bit?

SketchUp has been only 64-bit for many years. It may be that the uninstaller is still 32-bit.

there is way to look up how many the bits with the windows default program uninstaller?

What difference does it make?