Issue with Opacity and % to Double

When I try to define an Opacity on my Windows Form I get the Console Error:
PS C:\Users\USERNAME\Desktop> Cancel
PS G:\Documents> Ausnahme beim Festlegen von “Opacity”: “Der Wert “System.Object[]” vom Typ “System.Object[]” kann nicht in den Typ
“System.Double” konvertiert werden.”
In G:\Documents\WindowsPowerShell\Scripts\Spielwiese\test2.designer.ps1:22 Zeichen:1
+ $Form1.Opacity = [System.Double]0,8
+ ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
+ CategoryInfo : NotSpecified: (:slight_smile: [], SetValueInvocationException
+ FullyQualifiedErrorId : ExceptionWhenSetting

I take a look at the Source Code from the Form and PSScriptPad uses 0, for the Opacity and not 0.
I think this can be maybe an Bug at the it.
Or maybe im completely wrong.

Best Regards