wow! HUGE field! how cool is that.
it appears that the two lead women lapped everyone once and then lapped a handful of women twice. however, it looks like the results don't indicate that (ie they missed the 1 lap for most of the field and the women who were noted as 1 lap down should have been 2 laps down).
in general, the race is timed so that the lead riders in the fastest field (if there are combined fields run together) will race for approximately the race time (40 mins, 45 mins, whatever). if there's not much time between races, the officials will make sure that the lead riders finish short of the posted time by the amount of an average lap (8 mins, 9 mins, etc). this ensures that the slowest riders will finish racing in time for the next race to begin on time.
once the bell lap has been run for the leaders, everyone behind them on the field also only races one more lap.
does this help at all?