the app is deleting the past Daily Read data and just showing the read data of the week !
it is so weird that the app is not supporting viewing your Read streak over the month or the year;
You should see you Read data at any point + viewing your top score (top amount of time you spend on a day reading)
for example:
this week I read Quran for X amount of time on each day.
once it is next week the data is deleted , and the chart is empty.