Maricopa County has 248,000 early ballots that arrived on Monday and Tuesday remaining to count, along with 10,000 provisional votes that were cast on Election Day.
However, Maricopa County officials could not estimate the number of early ballots that had been dropped off at polling places, which could increase the number of ballots left to count by another 100,000 to 200,000 on top of The Republic's 400,000 estimate.
https://www.azcentral.com/story/news/politics/elections/2020/11/04/least-400-k-ballots-left-count-arizona-republic-estimates-and-number-certainly-higher/6157997002/