% Margin calculation

Hello

I'm doing % margin calculation(row total /grand total) which seem doesnt work with below dax expression always getting 100% for every row., uploaded sample data file in dropbox. I'm doing 2 step calulation 

 attributes are

rows  : costcenter, employee, task

columns : month(time)

Measure column values

1 Task total = calculate (sum[value], values(taskname))

2) Grand total = calculate (sum[value], values(month))

3) divide (tasktotal, grandtotal).  

https://www.dropbox.com/scl/fi/yp19gc2xupc5zr64h2zy1/Margin-data.xlsx?dl=0&rlkey=klb107gzsucsazvyjjy0z8gp6

thanks

vs