'Scuse me for butting in, but absolute minimum fuel for landing is final reserve fuel = 30 minutes fuel holding at 1500ft.
You do not have to have anything over this.
In my company the flight crew have to shout 'Mayday / Pan' if they 'will / may' land with less than that, and file an ASR if they land with less than that - note land and not block with less than that, at the weight on the day.
Our Ground Engineering colleagues will raise their equivalent of an ASR if the aircraft blocks on with less than 30 mins fuel at max landing weight.
There can therefore be occasions when the Engineers will file an ASR and the pilots not.