Why is htop producing different reports than Activity Monitor?
In order to get accurate processes, cpu usage and accumulative time, the user running htop should be root. This is not the case with top, because it has the "set-user-ID-on-execution bit" (suid) set.

Execute sudo htop from your user terminal or if you trust your local users add the suid to the binary (# chmod u+s path-to-htop-binary).