The spelling in this article (at the time of writing) is all over the place.
> This is not the D day landing which happened in the
> Normandy beaches in June 1944 but a rehearsal to D day
> landing which killed more than 600 men in friendly fire.
> The second batch met with a fierce fire defensive position
> resulting in the killing of at least 400 soldiers.
> The E boats were driven off after reinforcements arrived
> but the damage is done, 300 more soldiers died in this day
> for D Day rehearsal.
I'm not great at math, but: 400+ + 300 > 600
That doesn't even seem to be the extent of the deaths caused by this operation [1].
It also seems that this article may have been partially/mostly sourced from Wikipedia (for example, look at the bullet points of recommendations in each) [1]. The Wikipedia article also reads better.