This basically means that your attack rolls to status, and if it succeeds, will apply its status to all monsters it hits.
Status is not determined on a per-monster basis. (I guess unless resistances are involved, then perhaps the roll values are modified by the resistance value and compared to a threshhold? I'll have to experiment more on this)
This was brought to my attention when I realised that monsters deal varying damage to shields depending on whether or not their status rolls succeed.
Silversaps on Depth 10 will break a level 10 Force Buckler if either of their status rolls succeed, but will not break it if both status rolls fail.
This also proves that statuses are applied after damage, as a shield broken in this way will never cause the wielder harm as only the stun/freeze is overflowing the shield's hp, no damage.
For weapons that can hit multiple times with one attack (like autoguns, shooting 6 times with each attack) each hit would be counted as a separate attack and would have separate rolls. I have a Fiery Pepperbox, and it doesn't always inflict fire on all monsters it hits when it inflicts fire on one (even for the same type of monster, meaning the have the same resistances), so each bullet from it would have a separate roll.