Our current algorithm for picking the number of notifications to display
when expanding the notifications relies on magic numbers.
Previously we only allowed for header and an estimate of maximum height of
notification container, this is not ideal as there is padding at the bottom
and top of the notification container
This adds a special number for padding.
The longer term fix though is to render the notification panel off screen
then grab the correct count, finally adding it back into view with.
This would allow for large fonts, small fonts, custom themes and much more.
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