These are vCenter metrics just google those metrics rather than looking in vROPS.
When you sent up Admission control policy, by default it is set to host tolerated 1. Which means it will allow you to use all the resources up to number of total host resources combined minus 1 host. If you put a percentage instead it will only let you use total amount of resources minus the percentage set.
For example. You have 10 host with 100GB of Memory each. That is 1,000 GB of total usable memory. If you set Memory failover shares to 25% you only have 750GB of usable memory.
If you use host tolerated 1, you would only have 1000GB - 100GB. Which is 900GB total memory