Bob C. I think the confusion your seeing is based on the way we (people) think of % complete and the way MS Project actually calculates it. As per MS:
“The % Complete fields contain the current status of a task, expressed as the percentage of the task’s duration that has been completed. You can enter percent complete, or you can have Project calculate it for you based on actual duration.”
Typically, we think of a 40 hour task that takes 1 week for example. In this case work effort is pretty much tied 1-1 with, and drives duration. As a result, %complete seems to work as our expectation of how it works. In your case however, you have 18 hours of work spread over 3 weeks so our expectation that %complete is based on hours of work completed doesn’t align with how MSP actually calculates it (which is duration based). As a result, %Complete numbers seem to make no sense. As you mentioned, if you increase the hours to match 100% allocation for 3 weeks, the %Complete now presents numbers you expected to see.