Notification Data of alerts

I’m evaluating Kaltura for a company and can’t find proper documentation for Notification Data object.
didn’t help.
The problem is default style of the alert is too ugly to be shown, see attachment. Kaltura overlay
I discovered that ‘message’ atrribute supports objects i.e. new Image(), but can’t get the title, borders and buttons invisible, maxWidth, minWidth have no effect on the alert.

Where can I find comprehensive documentation of Notification Data?
Thank you!