If you do want to drop 4 -97 cans (or any other store) from 4,5,7 & 8 in ripple pairs, set the number of release pulses to match the total number of weapons. By doing this the IFFCC will release 4 & 8 as a pair, then 5 and then 7 as singles but with the shortest possible delay.
The same goes if you only have 2 cans on 5 & 7, set to release 2 pairs and both will be released with a short delay.
That may be the RL case, but in DCS unpaired stations participating in pairs releases will use the release interval as specified in the profile and not the minimum value. For example releasing 5/7 as "PRS" with 990' spacing shows they impact 990' apart and not the minimum. This can have disastrous consequences if, for example, releasing CBUs from 4/8/5/7 as "RIP PRS, 4, 500'" Instead of two pairs of CBUs landing 500' apart, you will get a pair of CBUs, 500' spacing, a single CBU, another 500' spacing, and the final CBU. The footprint of the attack will grow by 250' in either direction (since it is centered on DMPI).
If you think of the DSMS quantity setting as setting the number of release signals the IFFCC will send out, rather than simply the quantity of weapons, it might make more sense.
I think that this is confusing. The number of release signals and the number of weapons are the same. That is unless you consider a simultaneous pulse to 4 and 8 to be one instead of two pulses. In either case it is correct to think of the QTY setting as the number of weapons to release. This is in contrast to the F-16 which operates on the pulse multiplied by single/pair setting. An F-16 set to RIP PRS, 2 will drop two pairs for a total of four bombs. This is different than the A-10 whose QTY setting refers to the total number of stores to be released.
Ripple pairs assumes paired stations, such as 1/11, 2/10, 3/9, 4/8. Having a bomb on 2 and 9 (or 5/7) for example can't be released as pairs. Requests from pairs involving a non-paired station will get an unpaired release. It will then go to the next priority station and attempt a paired release until it releases the specified quantity. The specified quantity is never exceeded to conform to the PRS setting. In other words RIP PRS, QTY 3 will drop three bombs, even if two pairs are available.
Single, ripple, pairs, ripple pairs are configured on the PROF page for that weapon profile. The station order and manner of these four schemes is not configurable.