There is no set amount of time that referees are instructed/supposed to add on for substitutions or cautions
The 30 second thing is a guidance more to clubs as to what they can expect to see added on for certain stoppages
What the referee is supposed to do is stop his watch & then start it again when he is ready for play to resume.
I myself thought 5 minutes seemed excessive but when you look at the substution of N’Zogbia that was made in time added on, that took over a minute & so the ref was spot on in adding the additional minute & 20 seconds on to the 5 minutes
I actually thought Mariner got a few big decisions wrong yesterday – Stoke should have been awarded 2 penalties (the first when Figueroa hacked someone down just inside the area & the second when Alcaraz jumped on to the back of someone – the 3rd claim they had was a good challenge) & Latics should have been awarded one for Pennant’s challenge on N’Zogbia