On steemit your maximum voting capacity is 20% every 24 hours. HOWEVER, it trickles back every block (approx every 3 seconds), so using this we feature we can actually get SLIGHTLY above 20% per 24 hours when operating at above 100% target efficiency.
When you up vote manually below 98% Voting Power, ShadowBot will wait until it hits 100% again OR 5 hours has past since the last time ShadowBot voted for your account, at which point it consumes ~2% Voting Power.
If you vote more often you will see your voting efficiency in ShadowBot go down since it is voting less for you, and if you vote to often while using ShadowBot your Voting Power will never have a chance to recharge and eventually will hit 0 (though we disable your account once VP falls below 5%)!