Currently, the 'Count' Property shared by both the Star and the RegularPolygon fail to key their 'Count' Property within a Timeline.
Their 'Ratio' and 'Radius' Properties however do key properly/as expected.

Video attached.

Repro Steps:

1) Create a Page containing a MainPage.xaml
2) Introduce a Star shape to the RootGrid.
3) Create a Storyboard

4) On Frame 0, change the 'Count' of the Star shape to '3'.

Observe how when input, the value 'snaps' back to its original value.

5) In the Timeline, select the keyframe (diamond).

Observe how in the keyframe's Properties Panel, it displays a value of '0' versus having shown the Count's origin value with the Element itself selected.

6) At the 1s mark, click-and-drag the input field of the 'Count' shape using [Shift+Click&Drag].

Observe how on-release, the value 'snaps' back to its original value.

7) Save all documents, and re-open MainPage.xaml

8) Re-Open the Storyboard created in Step 3).

9) At the 0s mark, click the Element in the Navigator, and observe its 'Count' Value in the Properties Panel.

Observe how the value display the original Value of the Star's 'Count'

10) At the 0s mark, click the Star's 'Count' keyframe (diamond) in the timeline.

Observe how in they keyframe's Properties Panel, this value displays the value that was manually input in step 4).

Expected Results: Shapes 'Count' Values can be successfully keyed in a Timeline. (Whether interpolated or not is a different subject)
Expected Results: There is consistency between the Count Property Value when selecting the Element vs the its Timeline Keyframe at the same timestamp.