I suppose it depends on whether you read all the instructions first... or whether you read an instruction, follow it, and then read the next instruction.
"Plug it in"
OK... hmm... find an open socket... and... ah! Great.
"Wait 4-5 minutes"
OK... find a clock... it's 8:56... so... around 9:00 or 9:01...
Presumably the interval elapsed between plugging it in and the correct temperature being reached is slightly over five minutes. But if the user is treating the instructions as a scripted language to be interpreted at runtime, the additional read-next-step-find-a-clock
etc. means they only have to wait for slightly under five minutes.