Advanced find opens two windows

Hi,

I went into User section by,

Settings > Security > User (Dynamic CRM 2015 on premise)

In the User page when I clicked advanced find, two windows opens,

1. With entity User (Normal)

2. With entity Activities (First entity name in look for dropdown. Weird)

I have observed the same thing in every section of Security (Teams, Security roles etc)

Any idea, why this is happening. Please help me.