Ok, so I was all set up to produce 3 Sprints in a factory; proper number of workers, proper amount of mats, everything was good to go.
On the queue, the ETA read as 52-55 days for completion, but once I clicked start, the ETA changed to 102 days. Did I do something incorrectly?
When I started some more Sprints in another factory, with everything the same, I got a 53 day ETA. I've never had queue ETA change that much after starting production, hence my confusion.