Price amount generate back to 0.00 on Billing link after posting on Billing Review

Good day, I was testing the billing for different contracts.
I was testing the billing for retainer hours services. I added time on a sample ticket I created, and ready to post the hours on the billing review. Instead of posting the retainer hours on the retainer link on the billing review, I was using the labor hours link in the billing review. This is to monitor the actual hours used in a month, so I choose to use the retainer hours contract for that. Now here's the problem I encountered.

After I post the Labor hours on the billing review page with 5$ price per hour, when viewing the details on the billing link, the price amount generated was 0.00.
It should show the 5$ amount that I posted from the billing review right?

Can someone help me with this?