I really don't want to say how one should use the meter and arrive at the exposure he/she wants. I simply first show the OP how to calculate the average of several spot readings in the fashion that a meter with that function would do. I don't say it's a good or bad approach. I did make a comment that if you average a lot of readings then you come up with the same reading as if you use a wide angle averaging meter instead of a spot meter.