Why does chess.com say white is plus 3 here when white has a mate in one?

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bazoo123

Why does chess.com say white is plus 3 here when white has a mate in one Qg7?

https://www.chess.com/play/computer?moveList=e2e4%20e7e5%20g1f3%20b8c6%20f1c4%20f8c5%20e1g1%20g8f6%20b1c3%20e8g8%20f3g5%20f6g4%20d1g4%20d7d6%20g4g3%20c8e6%20c4e6%20h7h6%20e6f7%20g8h8%20g5e6%20d8e7&black=0&color=white&fen=rnbqkbnr/pppppppp/8/8/8/8/PPPPPPPP/RNBQKBNR%20w%20KQkq%20-%200%201

 

Note- if anybody is thinking "how is he beating an engine?  I am not.. That game was played me vs my opponent and then I went to play the rest against the computer just before my opponent lost.

 

Incase you can'ts ee that part of the screen

i5qfMFj.png

olsionh

Weird, it says M1 to me.

magipi

A reasonable explanation: white was +3. In the last move, black blundered mate-in-1, and the bar on the left side had no time to refresh yet.