Generally, when describing a thing, the unit is written as singular. "15 minute delay", "10 foot pole", "5 gallon bucket". When referring the unit itself though, it would be plural: "a delay of 15 minutes", "the pole is 10 feet long", "this bucket holds 5 gallons". I'm sure there's a more precise way to say this, but hopefully it helps.

[–] maniclucky@lemmy.world 3 points 1 week ago

In the first case, the subject (object? I always get them confused) is delay (which is singular), and the adjective is "15 minute".

In the second, the thing is "minutes" (plural) modified by "15".

[–] tyler@programming.dev 0 points 1 week ago (1 children)

The delay is singular. So one delay for fifteen minutes is a fifteen minute delay.

[–] Klear@sh.itjust.works 2 points 1 week ago

Not sure what that has to do with anything. Two delays are plural but two delays for fifteen minutes each would still be "two fifteen minute delays".