Isometric training can entail some trial and error to get the weight right. Coming to a dead stop—and maintaining that position—is harder than it looks, right? Taper the weight down slightly if you have to; a few pounds is a small sacrifice to make for the gains you'll see later.
Today is the last day you have to do isometrics during this trainer, so milk those 1-2-3 counts for all they're worth! You'll have two days to recover afterward, so this is no time to hold back.