z index value for floating social

Hello. I mistakenly edited the "z index" setting for the Floating Social plugin. If I go with too low of an index, the social box does not appear at all. If I go with a high number, like 1000000, then the box is always in the foreground, and even the admin bar drop down menus appear *behind* the box. I'll post a screenshot.

I am looking for the ideal number where the box will show, but will be behind all menu elements in the admin bar. It's probably the default value, which, obviously, I did not write down before editing.