Confusion about averages: If a person uses 20 cans of paint in 0.8 days, how can they average 25 cans per day when they have only used 20 cans so far?

Question

I'm confused about averages.

Say a person uses 20 cans of paint, in 5 days. That would that they use 4 cans of paint per day on average

But if a person uses 20 cans of paint in 0.8 days (current day), does that mean they use 25 cans of paint per day on average?

How does that work, since they have only used 20 cans of paint up to that point in the day?