i think they figure DE days like this...
take your max weight * .6
then take the 60% and * .3 and that should give you your band weight
in other words if you bench 300
300 * .6 = 180 180 * .3 = 54
so a 300 lb bencher should have 50 lbs of band tension at the top. this is the idea that i got. so you'd have 130lbs on the bar and 50 lbs of band.
but to answer your question...if you want to do the weight then do it. so long as you feel like it's fast enough keep it there. if you feel you need to lighten it then do it. i can't tell you because i can't see you lifting. going on your words then i would guess that you might want to go the lighter weight until you are pounding out the reps really fast and at that point you should switch to the higher. if you must err, do it on the lighter side.