If i'm understanding the solution the way softus is then One is correct as it doesnt state that you cant turn it over when wet,although this would damage the work done but in that case you could also say unlimited as you could carry on putting coat after coat on as that wasnt stated either.
Unless its one very very very very very long session
Not quite. The question asked how many sessions were needed to complete the door painting. One was done, and it needed two in total, so it needed one more to complete it.