Because steem_per_mvests growth at https://steemit.com you can see that your Steem Power growth because https://steemit.com shows it in STEEMs, but real SP value still same, if you want to know your real SP please check here: https://steemd.com/@beervangeer
SP doesn't grows dayly automatically, it's grows only when you receives rewards for your posts or your curation, and looks like:
beervangeer author reward: 51.743 SBD and 1.058M VESTS for @beervangeer/what-when-steemit-hits-africa… 18 hours ago
im not talking about the rewards. the SP is also growing, even when you are not active, but just holding SP