Since recent updates, the rain accumulation shows this scale in the browser version
C82291C7-7EF4-4763-B0F6-73442A630B0C.jpeg
And the same in the mobile app.
In both versions, the max display is 300 mm. So you need to update your app.
However, 1m is correct. This layer shows the rain accumulation up to 10 days and tropical areas can receive 1m = 1000 mm of rain and more for a week.
Currently, many locations are expecting more than 400mm over the next 10 days.
And for example this old screenshot shows much more than 1000mm
w/customized color scale
374E626D-56AF-46C4-BC9D-956EEEF2AC5C.jpeg