Alenka --
What you see is definitely one big disadvantage of using Proposals. In the
Project Center, the system does assume that Work = Duration x 8 hours per
day. This is obviously a flaw in the system, which is why I recommend that
you do not show Proposals on the Project Center page. To hide them, click
the Settings button and select View Options. In the View Options pane,
deselect the "Show Proposals and Activities" option.
You actually see the Resource Plan hours from the Resource Center page, by
selecting the resources in the Resource Plan and then clicking the View
Assignments button. Also, after you convert the Proposal to an enterprise
project, remember to reset the enterprise project to calculate availability
from the project and not from the Proposal.
Hope this helps.