I found a British site that said 3-7 days. Does that match anyone's data?

Jim

Phyllis and Jim Hurley wrote:
Phyllis and I tried putting a blue filter mat in the pond when we began
to see foam by the streams. Thought it might reflect koi spawning.
Turns out to be right! Eggs on the mat. Moved them to our new 400 gal
berm veggie filter.

Does anyone know how long it takes them to hatch?

TIA

Jim