How is “Average Profit per Million 30 seconds post execution” calculated?

Avg ppm @ 30s is calculated by comparing the price of the trade vs the price that would have been achieved if the trade happened 30s later (ie same side of the spread).

Example: if you buy 1,000,000 at 1.002 and 30s later the spread is 1.003-1.005 then

ppm =  1,000,000 * (1.005 – 1.002) / 1.002= 2,994

We only compute ppm at pre-defined  intervals (typically -10s, -5s, +1s, +2s, +3s, +5s, +10s, +30s)