Media not complete means that not all the media in Ancestry have been transferred to FTM. As I said earlier (I'm getting lost in this Forum because I can't keep up due to the time difference between UK ans NZ), running the report in FTM called Media Usage report and finding the media that are not linked could give you the answer. To run this report go to Publish, (across the top of FTM), click on Media Report, click on Media Usage Report and follow my previous 'instructions'.
In Ancestry, select the tree you are working with, then select Home. in the middle of the Home page and near the top you should see the heading About this tree with counts underneath. That tells me how many people I have and how many photos. "Photos' means all the jpg files I have attached to the Ancestry tree.
Go to the tree, at top left you'll see the name of the tree and an arrow, select the arrow and select Tree Overview, the numbers under the heading of Summary match those on the Home page.
Media in Ancestry is, as mentioned earlier (not by me), everything you have attached to the tree yourself. Photos, PDFs, etc. If you go to Gallery in a person and click Show, you will see you can filter by Media type. Records are not synced into FTM.
In the Help for FTM, in What's new in Family Tree Maker then in Family Sync you will find a detailed explanation for the type of media that do not sync.
If you are still wanting help/clarification from me, is there is some way we can private message? I find email is a far better medium for me to interact with people. However, you might want to learn by trial and error in the same way as i have done for about 11 years.