Quinella odds are calcualated on the Sega by multiplying the actual single horse win odds together and dividing by 2.
For example, 2 horses that are 10-1 and 20-1 would result in a quinella of 10x20/2 therefore = 100
Of course on many of the smaller odds horses the displayed number has been rounded off. Meaning that a 3-1 horse and a 10 to-1 horse may not actually pay 3x10/2= 15 it may pay anywhere from 12-18.
With the numbers provided in the races you displayed, the longest payout combinations were 20x30 which pays 300. There must be other times then when the numbers on your machine shift and display the traditional and more common odds scenarios.