The Part Kits tab shows both the part kits and all associated parts underneath.
If you change the sales package on the proposal, the part kits from the new sales package will be pulled in and any older part kits will be removed from the proposal. Doing this will give a confirmation message:
Are you sure you want to change the current Sales Package? All Items, Parts, Part Kits, or RMRs associated with the current Sales Package will be removed.
The Charges tab includes the part kit parts.
The Overview tab displays the part kit amounts and costs, which are also included in the cost of the parts.