Retention Calculation not working

Hi,

I am trying to generate retention amounts and I can´t, I am doing the next steps:

1.  Setup of the project has Retention format and retention billing format

2. In retention of the project I have entered a withholding terms at project level with a percentaje of 10 and a date that is the first day of the project.

3. I have enter a billing event with an amount of 1000, I suppose the retention will withheld 100

4. I run the generate draft invoices but the invoices is made for 1000 and not 900

Am I doing something wrong or do I missed some step?

Thanks!