On 1.8.8:

When I run /fill ~5 ~5 ~5 ~-5 ~-5 ~-5 air It creates a big hole like it's supposed too.

On the snapshots:

When I run /fill ~5 ~5 ~5 ~-5 ~-5 ~-5 air or any other block it says:
The number you have entered (-1.0) is too small, it must be at least 0. And doesn't actually fill anything.