It's a rather limited function, documentation is bleak...

I would suggest that you read the help screen - press F1 with the Optimize Inventory Screen open.
Some pointers: in Reorder Quantities you have to set "Reorder for" to Specific Location, it will not work for All Locations. In IC Setup Options Optimizer set Sales Periods to something other than 1, say 6. The run Year/Period you select is important - read the help screen.
With all that said, I spent a fair amount of time trying to figure this out with a client and we never determined what it actually does. There were no results that make sense.

Thanks - I had looked at the help, and saw nothing that helped. It is set up as it is supposed to be from what I can tell. I saw elsewhere there there was talk of an updated PU3 help file, but it looks like that never happened.
I will take your word that it was a waste of time and give up. Too bad, it looked like it might have promise.

Yes it's too bad that it is poorly documented and seems of little use. Maybe I'm wrong and someone else has some insight.

In the I/C Reorder Quantities, ensure that you have a Period Start for the month that you are processing for. i.e., for August, enter 08/01 for each location that you wish to update the Min/Max values for. If you then have a Minimum and Maximum Quantities values set in this function, these values should be brought in to the Optimize Inventory function when you choose that Item # and same Year/Period, Location and click the Go button. There is some Help in the Notes section for the main Optimize Inventory Screen and also when you select Related Tasks link for "Optimizing Item Reorder Quantities". Hope this helps.

So then it is really of not much use as 49153 noted. We only have one reorder sales period - no seasonal items - so all our Reorder Quantities are set based on a period starting 01/01. This would explain however why it doesn't work for us.

It should pick up reorder qtys if you only have 01/01, I can't remember the details but that is what we used in our testing.
Anyway there is no harm in testing all options.