Tanks sensor showing percentage - need to calculate consumption and estimate of autonomy in days

Hi

for my camper/rv I’d like to be able to calculate my past days water consumption and guesstimate how many days of autonomy I will have.

My sensors report tank level in percentage.

Can anyone suggest how I can calculate an average consumption of the past 2 days? tried looking at history stats or utility meter but not sure where to start from.

Thanks