I think maybe he is saying he only had to press and hold the shutter release on the D5100 and t would fire three time for the bracket and with the D5300 he actually has to press the button three times.
if that is what you are saying then do you have it set to Continuous High?
I didn't realise this, I just presumed it would take the longest exp shot and work back from that for eg if I did a 3 sec shit it would take a reading at 1 and 2 secs giving 3 shots..