As someone who has operated Skydiving in Class C and in Class G and Mixtures of both, personally theres a few distinctions. "Parachutes" is the number of Actual Parachutes, you might have 5 POB but there might be 2 Tandems therefore its 2 Chutes. The number shouldn't really matter for a normal Tandem Load as they'll all pile out together in a quick fashion.
Becomes a different story for doing student jumps as they can take a bit longer as sometimes students freeze up or hesitate and you'll have to do a second run to dump them out, but i'm not sure if controllers would even be aware of that, when that did happen to me i'd always call Centre and let them know that we'd be an extra minute or two to keep them in the loop as we operated inbetween 1 large very active (Read student flights) aerodrome and another similar sized aerodrome that had plenty of IFR and in the vicinity of an International/Domestic airport, but that was less of an issue as we didn't do jumps above 10,000 at that dropzone.
The controllers we "dealt with"/"put up with us" at my first Dropzone which was Class C above 8,000 and sometimes Military Controlled above 3,000 were a pretty good bunch, they always knew what we were doing and we kept them informed so they didn't hold us up and we didn't bother them! Every now and then we'd have an IFR aircraft coming within 10nm of the dropzone, but they'd just clear us and give that aircraft a heading to keep them outside the 3nm area we were cleared to drop in, never had a problem with them steering anyone 10-20nm away as some others have described, but they were generally small - medium Twins on Charter or Training, not RPT.
Its always interesting though when you're already Chutes Away and the controller reports a transponder squawking 1200 has just suddenly appeared and heading towards the area... just gotta hope and pray the guy is on the right frequency and hears you when you tell him hes tracking directly for an active dropzone with chutes on their way!!