Oh, that one is very irritating.
It took me a while to understand 0.2% proof stress as nobody would explain it properly
This is how it works.
Where your strain is (on the x-axis) for your FIRST value, simply put a dot 0.2% of your first strain value
(NOTE THIS SHOULD BARELY BE OFF THE ORIGIN)
Then draw a line parrallel to the elastic region going through this dot your marked previosly
Then where your line hits the curve. (Record the stress value at that point)
And thats your 0.2% proof stress
I advise that you look up ALL your answers on wikipedia, and just put your figures slightly off.
Worked for me