I reckon people have misunderstood this question.
Low game is simple but "high" low game -- is not high game -- it is your best low game in any given series eg.....
170, 200, 160 == 530
155, 210, 165 == 530
high low game is the 155 game (at least that's how i read the question - i know that Jess has bowled higher games than 143 but that is her "high low" game.
My low game is 72 and my "high low" game is 236 which i have done twice