1. The Decimal Separator and Thousand Separator separates the thousand values globally in the charts. A simple (.) Dot in the value option separates the decimal from values.

2. In above figure the Thousand Separator has a toggle button, if you click it then the function appears as figure below:

3. Thousand separator is just a (,) comma, which is used to separate the thousand values globally (for value axis only) in AIV charts.