Shows huge percentages for dropbox but total is normal, and everything seems to be running fine. I have a Macbook with Intel Core2Duo
On OS X, 3,000% CPU would mean thirty processors are being fully used. I'm fairly certain that no Mac has ever shipped with thirty cores (even with hyperthreading), so this is not correct, particularly on a Core 2 Duo MacBook.
The counters that track usage can get messed up like anything else. If it is something that happens each and every reboot we can dig into it a bit, but most of the time it's a signal to reboot and let the OS tidy things up.
The goal is on a two core processor, if one deopbox thread is running all the time, you get dropbox at 100% usage. Due to inefficiencies and delays due to interrupts, a multithreades process that is taking all the CPU can approach 200% but usually not reach thy perfect limit.
Here the math is adding up the threads improperly. A 12 core Mac Pro with two threads per core could perhaps have something near 2400% so the program has to be able to show such "ridiculous" numbers just in case it happens.