Hi
The POT is really just a bottom line indicator, but its components Win S/R, Loss S/R and avg odds do provide the information needed in finding your confidence level, your Optimum edge, your bankroll growth rate and longest losing sequence, which are very important tools.
The other use of the POT apart from the obvious, is in providing a roadworthy test on a system or whatever by adding one's # of bets not over a year but a shorter duration, you can get a Final indicator of that systems roadworthyness

"Could someone explain this; if you know you'll bet (roughly) 500 times next year (only on the most "profitable" type of horse) and will make (roughly) 10%, how can you make any more ACTUAL money except by INCREASING the amount you wager??? Cheers,and good luck from (a baffled???)"

If you have enough past records of your betting history, yes you could make more money without increasing the avg amount wagered within a yr, simply by knowing something called deviation from the Equipartition, overseas betting groups run massive amounts of sim's based Equipartition an Pascals Triangle to adjust the amounts wagered within a betting series, thus not increasing bet amounts overal, but by combining the above knowledge with ones Optimum edge, they reduce risk at certain times an increase reward at other times, without increasing ones avg amount invested for the set time period.