Calculate Column

Hello,

I create a new column (TOTAL DAYS DELAY Design) to calculate days number between two Date columns. If the 2 dates differed I can see how many days in between. If not the cell is empty and this is perfect.

But the problem is I created an other column (Respecting Date) to show if the anticipated date is the same of the delivery date or if not. If the 2 dates are same and no difference in the column TOTAL DAYS DELAY Design (empty cell)  put 1 in the column Respecting Date and if not put 0. I have to calculate how many projects respecting the anticipated dates and give a % on the total of project.

Respecting date (new column) = IF('Design Estimate'[TOTAL DELAYS DAYS Design] < 1, 1, 0)

Can you let me what is wrong in this measure, please.