The ERUF value that you calculate is not a response time. It is just a number that allows you to compare your applications with recommendations made in this manual, and with applications that you have already created.
It is in an indication that what you want to do is "fair and reasonable" in terms of resource utilization, and allows you to relate the resource requirements to other functions that you have created.
For instance, if you have many transactions with ERUF=4 values and they work well, then it is very likely that a new transaction with ERUF=5 will work almost as well, but a transaction with ERUF=12 will take about 3 times as long to complete.
