I thought at one point you mentioned you are new to SAP CCS. Here's some basic info that might help you figure out what's going on...
If you know the installation that had a meter change, you can look at table EASTL to see the time slices relative to the activity. Using the logical device number from EASTL, go to table EGERH to get the associated equipment numbers. Notice that the time slices are the same. The equipment number is unique to the device. Using the equipment number and installation, you can go to tables EABL and EABLG to get the meter reading data.
Keep in mind that a meter removed from one installation is probably eventually installed on another installation (different premise) later, so you have to be careful with the time slices to ensure you are getting the right data. This means that any given equipment/device number can have data for more than one installation over its lifetime.
Here are some of the table relationships:
EANL->EASTL->EGERH->EZUZ/EZUG/EGERS->EQUI
EANL->EASTS->ETDZ->EASTI
EANL->EABLG->EABL
EABL->ETDZ
ETDZ->EZUZ
It might help to look at the contents of these tables to see how the data looks in its raw form. If you run SE16 on table EASTL for a bis <> 12/31/9999, you should be able to find installations that have had meter replacements. Find an installation, go back to the beginning and re-search using the installation. That will show you the various logical device numbers involved that can then be used in the other tables to work your way through to the meter reading data. After this, use some of those specific data examples to manually run the function modules you are using in your report in SE37 to see what data comes back and how it looks. Hopefully that will reveal where it's not matching up.
K--