This happens when e. g. viewing template items, selecting some of them and then selecting a linked template from the list. Works the same way with triggers, discovery rules etc.

Steps to reproduce (with default template set):

1. Go to "Configuration" -> "Templates".
2. Click "Items" of "Template OS Linux".
3. Select all items.
4. The "Go" button should show the number of selected items, e. g. "Go (32)".
5. Find an item from linked template and click the template name, e. g. " Template App Zabbix Agent".
6. The view switches to a new list of items but the button still shows "Go (32)". Selecting all items now adds their count to "32".

Observed in trunk, did not check neither 1.8 nor 2.0 .