Instances count on overview page doesn't take default visibility into account

The count that is displayed on the `Instances` tile will not always match the number of rows in the table on the page the user is directed to by clicking it.

The table on the instances page has a default time-range filter applied, but the instances count on the tile doesn't take that into account.

Simply applying the filter to the count on the tile as well might not be the right solution because then the numbers of the three tiles `Instances`, `Online`, and `Offline` might not add up, which is also confusing.