You use the scale that has a number that is the same as the number on the switch setting...disregarding the decimal point.
You only measure amps by selecting the proper mamp scale which is greater than what you expect from your circuit. You insert the meter leads between the source (transformer) and the load (resistor, bulb, what have you). The other lead of the transformer goes directly to the other side of the load. Then you will read the current (mamps) that the load draws (not the limit of the transformer which is what you refer to...2000mamp). Keep in mind that if your load is a short or draws more current than the meter is capable of measuring, you will usually blow a fuse inside the meter. I am guessing (since your picture has too much glare to read the dials) that your meter has a limit of 250 mamp.
