Burn down calculation

Hi,

I need help with figuring out a DAX formula to do the Burn down of a column depending on Priorité not date column.

https://drive.google.com/drive/folders/1nuZ965fBcIEqNcYFw0e-C9AmDusk5RIx?usp=sharing

In the link i put mock pbix file and an Excel file where there is an exemple of the Out come in column J

Thanks in advance