All Ubuntu machines (all versions) I know has those appearing in htop (mine has, servers have) and the number shown is 0,2 which means 0.2% and not 20% (htop reports are already in %). Anyways as Gilles said before they are not effectively running.mysqld do the same thing on mysql servers (not 60 but a lot) each reporting they are eating a good part of RAM (like 20 or 30% each) and that is not possible. You can check the free memory and you'll see they are not using this RAM.