Sorry for the delay responding to this. The short answer is that I think your setting will work. "Time interval for new test versions" is the way the system figures out what the number of tests means—essentially, the setting "number of tests per time interval" is a rate, and "time interval for new versions" sets the unit for the time.
A good example for how this can work may be our gateway testing. We want students to take the proctored version of the test at most twice per day, but they can make those two attempts any time that we have proctors available (roughly 11am--10pm). For this, we set
Time interval for new versions = 720 minutes Number of tests per time interval = 2
(720 minutes = 12 hours, which accomplishes our goals). This is explained with what may or may not be any real clarity on this wiki page.