Update Firefox to 31.0 via about->check update accidentally..

I am using Portable Firefox for web development.

Today i want to upgrade my local installed version Firefox to 31, but i pick the wrong short cut point to portable one and update via about menu.

After restart i know i am doing wrong, but the portable Firefox update success to v31.0 and it work fine.

So what is the negative effect if i do it via about->check update?
Just wonder what the build-in updater actually do to my system? (write registry, leave some file, create another profile etc.)

I use portable Firefox long long time from Firefox 5(?), i know i must update by install over the same portable Firefox directory.