Sort:  

then why does it go down when you power down, and why is the total always the exact voting power you have?

Delegated SP is included into your VP but you can't take it out. Because it's delegated meaning not yours and you got it from someone to use for a specific amount of time.

There is no way that you can take out delegated SP, only your own.

The delegation lowers by STEEM itself the more SP I gain while I power down.