You can combine all 4 conditions into "Or" block, it will be a bit bulky but it will be one event.
Or you can change all four condition to this one:
System -> Compare two values-> (bgg=7 | bgg=14 | bgg=21 | bgg=28) = 1
TakHarf On frame changed -> Set WallpaperCount to (TakHarf.AnimationFrame>7 ? (TakHarf.AnimationFrame-7) : TakHarf.AnimationFrame)
(if there are no more than 14 frames in this animation)