To create log book entries form multiple volunteers at one, use the "Add Hours" feature.
You can access this from the left menu.
Select the records that you want to create hours for.
First decided what to do if a volunteer is not already placed:
Then select the opportunity:
Enter Start Time and End Time. The tab to the "Hours" field and the system will automatically calculate the time:
Chose the Date:
Then Save (or check Create Another and Save to create multiple entries):