I am saying that the system should fail in terms of SLA even at 99. In the link I shared there is a simple worked example of 10.3 capacity/hr for 10 events/hr

I am saying that the system should fail in terms of SLA even at 99. In the link I shared there is a simple worked example of 10.3 capacity/hr for 10 events/hr that piles up 28 events. It also shows the problem can be mitigated by analysing it in queuing/probabilistic terms. In real life it is even more complicated obviously!