SgtPsycho: It's been a while I do seem to recall there's an issue with spawning there. Usually I do a loop of he supermarket, go out, clear another area, then come back. Usually (I think) there's more monsters and that's how to get a perfect clear.
Three runs through the mission, hour and half, Sigma Team -- the heck, did Nikolay ate your tester's brain?
TL;DR for anyone wandering around: can confirm.
As you know, "Reloaded" version contains incomplete and seemingly untested missions (this one and next one, I think you noticed the lack of music), so I just roamed around the level (on a car, thought there is a trigger tied to it) but on the second loop (35 minutes, not 25-30) there was more (exactly 31) monsters in the store.
I think I should get back in my childhood and open AS2 mission editor (it's free and can be found on dev's forum) or just search and talk through for already existing solution to help anyone trying to get perfect 100% monsters/secrets walkthrough. If I do -- I post here. If I not -- well, ping me and say "саня задолбал" (: