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WRONG on both counts
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No I'm not a POM, a 4th generation Australian and:

POT is another name for ROI (UK term)
ROI or POT - Short for 'Return On Investment'or'Profit on Turnover' in percentage (%). The formula: = total profit / total staked * 100.
Example: if a series of 55 bets (all at $1 stake each) returned a profit of $7.50, then ROI/POT% = $7.50 (total profit) divided by $55 (total staked) multiplied by 100 = 13.6% ROI/POT

POS - 'Profit on Stake' in percentage (%). The formula: = total profit / initial stake * 100.
Example: if a series of 55 bets(all at $1 stake each) return a profit of $7.50, then POS% = $7.50 (total profit) divided by $1 (initial stake) multiplied by 100 = 750% POS


POS, ROI & POT all have the same result after one event. POS differs from ROI & POT after more than one event because POS is always based on the initial stake as the divisor.
RP