How to convert 220 volts AC into 12 volts DC using a transformer?
12.4V / 24.9ohm = 0.5A which is what your Amp meter shows.
If you want more current, ex 5 Amps, you should decrease your R Load to about 2.4ohm.
Note as you pull more current you will have more voltage drop on the transformer so it's not exactly linear.