Bundle does not always show 7 items when there's more than 8 items in the bundle

The bundle sometimes doesn't show 7 items.

In the example, I put 9 items in the bundle. I start with an empty bundle. I add 8 items, these show perfectly. But when I add another item it only shows 4 items. The other 5 are hidden.

This should show 7 items with a '+2'.