Count Chart-Bar for a column

[ABBA]

I have the sheet in which the App creates an entry for a “PROBLEM”, its column heading and has a Date associated with that Problem. There are multiple dates for the same “Serial Number” but has a uniqueID.
I want to create a count of “Problems” but only the LAST ENTRY of the Serial Number and not double count

How can we do that?

[Steve]

So you want a count of distinct serial numbers?

COUNT(MyTable[Serial Number] - LIST())

Subtracting a second list from a first list has the side-effect of removing duplicates in the result.

[ABBA]

Thanks Steve
How can this be applied to a Chart Function as Bar Chart?
I have SLICED the data to filter out unwanted data and using that slice to plot the Bar Chart of Count
How can i get a Unique Count of Last Entry in the database, in Bar Chart?

So I guess I am looking for a Filter on Database[Well Serial] that will only give me Unique Last Entry for the latest data