From playing with several of them over the years, they just aren't that accurate and don't move as incrementally as you would think.
Once you reset them, they will usually go back to the previous setting after a hard pull.
Side Note: Removable air cleaners on DP's (non canister type) should never be removed to just inspect and should NEVER be blown out with air to get additional life. Either practice can get dirt/dust into the system which can quickly damage a diesel engine. Determine a mileage/time frame to change your air filter and stick with it.