Question about KPI cards' trend axis

Hi guys, I am developing KPI cards. 

The value here I am using is a DAX measure: 

and the start of week is a column from calendar dimension table:

However, I am not able to get the correct result on this visual. Because last week's total number of event should be 18.5K

I also tried to change the trend-axis to the 'Start of Month' column, whose result is 366 which is last day's total number of events instead of last month:

Note that I have closed the automatic date hierarchy settings, so all the date columns are not hierarchy field.

If you know the root cause, it is very appreciated if you can give me an advice. Thank you so much!