I don't know of a variable named specifically injus", there are these below:
for instant trip, injHiSec never gets incremented (the trip gets reset every half second) and injHius is the number of microseconds that the injector was open during the last 1/2 second.
PHP Code:
unsigned long injHiSec;// seconds the injector has been open
unsigned long injHius;// microseconds, fractional part of the injectors open
.75 is the latest version, just added some instant speed fixes in .74 and .75 was basically documentation only.