Don't - just specify the number of host failures you are able to tolerate. This will calculate the number for you - take a look here as a good reference: vSphere 6.5 what’s new - HA - Yellow Bricks
Also consider changing the "Performance degradation VMs tolerate" option away from 100% to 0% - especially useful if you don't have reservations in place on your VMs and want a level of comfort with a HA failure that performance should not be impacted with reduced hosts to run your workloads.