Counter base maintenance and multiple counter maintenance

Hi

With refering to the counter base order generated in the system, i have confused.

We have the plans 100, 200, 300 to max 2000 Hours. The task lists are assigned. The maintenance plan annual estimate is 4000 Hours (i dont know why its required if the measurment documents are in use) ..

The system is regularely generating the orders eventhough we have measurement docuements upto 300 Hours. Last week we have no measurement updates.

Can you give me the logic, functionality of the performance maintennace. I have read SAP help which is not explaining in practical manner.

Also how to work for multiple counter maintenance. We have to do for DAY (30 Days, 60 days. 180, 360 Days) Wise or Hour wise (300, 900, 1500, 3500, 7000 Hours maintenance. Can you tell me how to work for this on single maintennace plan..since our equipment also only one.