Yes when you delegate steem power (SP) that shows up as a negative value in your steem power delegation and so that amount of steem power is not part of your voting power as long as it is delegated. However I believe minnow booster is currently paying about 45% yearly interest and you receive SBD payments on a daily basis. There's also about 1 week waiting period to get the SP back when your delegation contract ends. Similar to a real world CD (Certificate of Deposit) Account.