Export shows diffrent numbers then page(unique Visitors)

Hallo Everyone,

I need youre help. I am trying to create a Matomo evaluation with Excel. For this I use the export function in the “Visitors” area.

During this process I encounter something odd. The total amount of unique visitors in my spreadsheet didn’t match the numbers on the Matomo site.

Screenshot as reference:

Is this a bug? The problem did occur on different sites. Can someone explain this behavior to me?

Thanks for youre Support