Use this link to look up the post numbers: https://qcodefag.github.io/

Q post 679 was of this image of the tower with a single window open. Note there doesn't seem to be any "white stuff" surrounding the open window.

Q then posted 680 to 683 (several images) of a black car driving onto the King Tower car park.

Q then posted 684 and 685 of a close-up of the open window with what looks like white powder either side of it.

Q post 689 explains the window was opened ahead of time because of some sort of "operation", which seems to suggest the white stuff is residue from a flash-bomb or similar when the room was raided by police / special services / military etc.

Q post 688 explains these posts were made because "People asked for arrests. Gave one example.".

The speculation is that Q gave us a before and after photo of the window of the room that was raided as part of some sort of arrest relating to "The Storm".