Test case:
1. Click on the first item and push Shift + Down 2 times. 2 items will be selected.
2. Then push Ctrl + Down 2 times and push Ctrl + Space. One more item will be selected and it will become an ancor.
3. Push Ctrl + Down 2 times and push Shift + Down.

It is expected that only items between the anchor and focused item will be selected (+1 item below focused item).
But as you may see previously selected items (above the achor) remain selected.