The adjusting screws only change the instantaneous trip setting. A breaker should only trip on instantaneous if there is a ground fault or a short circuit. Overloads only trip the thermal trip unit.
Mechanically, a breaker can be reset almost immediately after an instantaneous trip (not that it is a good thing to do.) After an overload (thermal) trip, the breaker needs to cool down before it can be reset.
If the CB is tripping and they are able to reset it, it probably is not a fault, just an overload. It is possible that the trip occurs when some motors or other loads have an inrush current that bumps the load current up to the instantaneous setting for 1/2 second. You would need to connect up a recorder to determine if that is happening.
Moving the loads sounds like the best approach.
On some breakers the 2-10X indicates an instantaneous trip setting of 2-10X the breaker rating, 1200-6,000 Amps in this case. Is there a load that could have a 1000A inrush?
But don't adjust the instantaneous unless you really, really know what you are doing.
The adjusting screw is part of the live parts on older breakers. We investigated a fatality where the insulating cover on the adjusting screw cracked or broke off. The electrician put his screwdriver in the hole and contacted the slotted screw mounted directly on the trip unit. The shaft was also touching the panel cover. The arc killed him and injured his helper. (25 years ago before arc flash awareness.) We found similar panels in other facilities with the same problem.