Step 1: Click on the date on which the opportunity happened as shown below.

Step 2: Go to the respective opportunity and click on “Manage Volunteers”.

Step 3: Now, Please click on the “clock” symbol which is on the extreme right side.

Step 4: Click on the “pencil” symbol as shown below.

Step 5: Enter the new ” hours” & “minutes” and click on “save” as shown below.