Bid Optimization Rate (can be called revshare on campaign) has been made in order to let you set the % not only on the Supply side, but on Demand as well. We subtract mentioned percentage on the campaign level from the bid in RTB campaign response and pass further to the publisher.
You can find this field in the RTB / Prebid Campaign Basic settings.
For example, you have set 30% as Bid Optimization Rate. It means that we will subtract this 30% from the bid in response and pass this response further to publisher:
5$ came as bid in the response, we subtract 30%: 5$-30%=3,5$ and pass this 3,5$ back to the publisher and recorded as a Total Revenue.
"Auto adjust" was made to automatically analyze discrepancy and adjust to the difference. This option is relevant only for entities that have external numbers fetched (via API) and used mostly for push/pop activity.