I had this charger. The numbers along the bottom tell you how many amps the battery is accepting from the charger. The needle is basically an ammeter.
There are 2 scales, one for the 2 amp rate (indicated by the small red triangle on the left) and one for the 10 amp rate (indicated by the 0-100% and starting at the "R" of "Rate" and ending at the far right).
If you are charging a low battery at the 2 amp rate, then the red/green triangle at the left applies to tell you how discharged (roughly) your battery is. If it is taking 2 amps at that rate, then your needle will be at the high end of the red triangle on the left showing that the battery is accepting all of the 2 amps being supplied by the 2 amp charger. This means you have a serviceable battery and it is really low. As the battery charges, it will start accepting less amps and the needle will move from the 2 amp rate towards the left showing a movement to 0 amps indicating a 100% charge
Same thing applies at the 10 amp rate, except in this case, the 0-100% scale applies. If the needle is pointing at the 25%/10 amp point, you have a good battery that is very discharged. As the battery charges, it will start accepting less amps and the needle will move towards the left showing a movement to 100% charge.
If you test your battery and you know it is very low and the charger indicates a very low amp flow nevertheless, you will know that your battery is not accepting a charge and you have a bad battery.
I had the manual version of this charger so I could tell whether it is on or not. Yours is automatic, so if it has detected that your battery is fully charged, presumably it would turn itself off and accordingly there would be no amp flow showing on the ammeter. I'm not sure how you would test this function. It looks like it is off. That could indicate a fully charged battery - with the automatic charger cut-out having been activated. I'm guessing on that one. If you think your battery is fully charged, I'd switch it to the 2 amp rate and leave it, given you have an automatic charger.
I hope this helps.