Well, very possibly even 24 hours would not be enough to fully charge on the 2 amp setting. No snarky tone intended.
I have a group 27 rated at 115 amp hours.(12.75"x6.75"x9") 62 lbs. Most starting batteries are much smaller and are around 84 A/h. I am not sure what size battery is in the OP's vehicle.
If MY battery were still newish and healthy but accidentally discharged 100% to 10.5 volts overnight, If I then put a 2 amp charger on it that actually puts out 2 amps , starting it at 10.5 volts(rested), it would not even be 50% charged after 24 hours.
If this battery was older and more sulfated it might only have 65 amps hours left, so then 2 amps for 24 hours would indeed bring it closer to 100%
And that is not including charging inefficiencies or the fact that the 2 amp charger is likely going to start tapering to 1 amp well before then.
A temperature corrected glass hydrometer is the best tool for a flooded battery.
A voltmeter a distant second, and relying on the accuracy of the ammeter on an old manual charger behind that.
My Manual Schumacher on the 10 amp setting has never gone above 7.5 amps according to my modern digital ammeter.
The 2 amp setting measured 1.8 amps when starting charging at 12.4 volts.
Think of an aging battery like a 15 gallon fuel tank which just keeps getting smaller with age.
After a few years, or a few months of abuse(chronic undercharging)
You can still fill it up, but it might only take 3 gallons to do so and then only has 2.5 gallons to dispense, and you need 1.5 gallons to start the engine.