Max Y Travel 470?

Hi, I have a question about the maximum Y-axis travel for the bed size. I have added a much longer rail under the bed, 1 meter to be exact, but it’s functionally 977.9 available for travel. I have tried putting that into the bed size, but it keeps telling me that the max is 470 and its confirmed in the info display. Is this hard-coded in Marlin, or is there a bug preventing the compiler from inserting the correct distance? I am also struggling with the display, as my icons are gone and it does show the cursor correctly. It was the DWIN stock.

I have realized that the display on the machine is the SYNWIT version, but I am still unsure which flavor of the display option I should choose to make it work.