A rejected ballot is not always a lost vote. Most states let you fix a problem with the envelope, and nationally 53.7% of flagged ballots were fixed in time and counted. That is 303,735 votes that would otherwise have been thrown out.
On a phone you can also long-press the map and save it straight to your photos.
Where the most ballots were flagged
The counties handling the most cures, and how many they saved. Your odds depend enormously on which county you are in, and the rules are the same within a state.
County
Flagged
Saved
Maricopa, Arizona
34,332
79.5%
Clark, Nevada
22,669
66.3%
Orange, California
21,640
48.5%
King, Washington
18,633
37.1%
Los Angeles, California
17,938
37.5%
Riverside, California
15,202
50.2%
Pima, Arizona
14,873
40.7%
Contra Costa, California
12,739
75.3%
San Bernardino, California
10,464
19.6%
Salt Lake, Utah
8,947
46.7%
Only 743 of 3,143 counties reported a cure process, so most of the map is hatched. That is the data being thin, not the counties doing nothing: a blank county has no statewide cure process, or did not report one. It never means nobody had a problem there.