A few things
Ads are not burning LEO this was the case way back when but right now the revenue is being pooled into a smart contract and at some point it will be used to buy LEO off the market and award it to those who are staking LEO tokens.
16% APR comes from buying the LEO again through the hive power generated. So it's selling Hive for LEO (at least that's my understanding)
Thanks for your answer!