What am I missing? Charging question

[66FBCharger]

I have a 69 Charger R/T 440. It has the voltage regulator that looks like the points style but has the electronics in it instead of the points.
The car has been sitting for about a month while I am doing carpet and interior. the dome light has been on while I work on the interior. Today I decided to take the car out for a shakedown before leaving for Carlisle Thursday. I put the battery on a slow charge for an hour before starting the engine and leaving the house. The ammeter shows about 10 amp charging and 15 amps on the highway. I drove about 20 miles or so and the reading doesn't see come back to zero.
I put a voltmeter on the battery while running. It reads 14.1 volts. I put a new regulator on and there is no difference. What do I check next? Bad ground? loose wire at ammeter? wiring? faulty alternator?
Thanks for your help.

[A383Wing]

sounds like battery is low....everything else seems fine

[66FBCharger]

How long will it take to go back to 0?  I am going to put the battery on the charger again for an hour.

[Pete in NH]

If you have a small battery charger, say 4 to 6 amps, it will take a while to charge a bigger battery. I would put the charger on it overnight and then see what the ammeter shows when the car is running. Say you have a 75 amp/hour battery and its down all the way, it would take a 4 amp charger over 18 hours to recharge the battery. I would leave the charger on the battery until the meter on the charger tapers back to an amp or two.

[66FBCharger]

You guys hit the nail on the head. I charged the battery for 2 hours or so on low, now the ammeter is at almost zero.
Thanks guys. I was worried I  had a bigger problem.