After clearing a group chat I still see storage usage for this group, why?

[iMore Question]

after clearing a group chat I still see storage usage for this group

Even though I have cleared a group's chat, so when displaying the group I get an empty screen, the storage usage option under settings - account - storage usage shows this group as my largest.

 

[cutdacheck2003]

Are you clearing the messages in the text instead of deleting the whole text?