You have presumably clicked accidentally on the field for inputting the current page number, or even on one of the four fields of the coordinates display. The input field that has appeared has no explicit [Cancel] or [OK] button. Normally you just have to input a number here and press the [Return] key.
There are many cases where this is undesirable (e.g. so as not to change existing frame dimensions).
With [Undo] you can close every Calamus dialog. In the SL WindowsPack the key [F12] is assigned to [Undo].