I can't open the link.

So I created the similar data. I used sum, you can try to change sum to count

count of s.issue_name = sum('Table'[Issue_name])

PROPORTION =
[count of s.issue_name]
    / CALCULATE ( SUM ( 'Table'[Issue_name] ), ALL ( 'Table' ) )

P2 =
VAR _PROPORTION = [PROPORTION]
RETURN
    CALCULATE (
        [PROPORTION],
        FILTER (
            ALL ( 'Table'[weeks_in_work] ),
            'Table'[weeks_in_work] <= MAX ( 'Table'[weeks_in_work] )
        )
    )