For a work setting, a quarter tab is Lots!
I once had that and had to give a presentation of some new software to a tech group.
That was slightly irresponsible on my part, although the situation was a known lost cause prior to going.
i was also imprisoned in a 2 hour speeding mercedes 240 SL road trip each way across the Canada US border with my client - and I did not enjoy either his driving nor his cowboy republican humor, and endless complaints about business, people, governments etc.
So for me it was really a silent protest and self indulgent withdrawal in a degenerating work relationship, on a day that was not a normal working day.
In any case I think drug use at work is not recommended.