The Additional Attack gives the character one more attack (i.e. roll) for every 10 ranks in the style, but also giving a -20 modifier to all attacks in a round for each attack beyond the first. This -20 to the OB is applied first thing, before any modifiers from specific maneuvers would be applied.
So, if you also had Shield Bash (will presume no Shield Training), and you declared that you were using your Additional Attack and your Shield Bash, then you would have 2 attacks at -20 to each and the Shield Bash, which would use 1/2 of your style OB (after the -20 from the Additional Attack), and another -20 for it being your off-hand. Please note that the "1/2 OB" for the shield bash is determined AFTER making adjustments for any specific maneuvers, but before the -20 offhand penalty is applied.
Thus, if you have an OB of 100 (and more than 10 ranks in the style), and you declare 2 attacks and a shield bash, your OBs would be 80 for each of the 2 attacks (before any adjustment for any specific maneuvers) and 20 for the shield bash (80/2=40 -20 (offhand) = 20). If you declared that your attacks were going to put 20 points into DB, then Your OBs would be 60 for each attack, and 10 for the shield bash.
How Additional Attacks interacts with Additional Attacks is slightly more problematic. The modifiers from the specific maneuvers are intended to be for the whole round. Therefore, if you have/use the Additional Attack, the extra attacks are going to have to be the same specific maneuver for all of the attacks.
The only way that different specific maneuvers should be allowed is IF those maneuvers had the same DB modifiers across the board.
For example, using the same situation as before (2 attacks and a shield bash). Our first attack is a Basic Swing, and our guy is still parrying 20 points into DB. His second attack can be another Basic Swing, or is could be a Riposte (with an OB mod of -20) -- or a Block, Defensive Block, or Defensive Strike (with their other adjustments made to match an adjustment of +20 ti DB -- the character does NOT get to set these adjustments, they are dictated by the first attack).
The point is that the second attack must have the same DB modifier as the first, and the second attack has to be legal for that specific maneuver (i.e. you cannot use 2 different maneuvers if one "requires" 100% activity), if it is different from the first.
Note: If the additional attack includes an initiative modifier, then I would apply that modifier to the following round, since initiative had already been determined for this round.
Adrenal Speed -- This skill gives you extra activity percentage to use. That means that you could make another attack declaration -- again -- the DB shift declaration would remain, and it would constrain your choices of actions, or this extra activity percentage could be used to allow use of one of the specific maneuvers that requires 100% activity, etc..
Note: It is important to remember that the Specific Maneuvers were designed so that only one would be used per round. On page 61 it tells you that no more than one specific maneuver may be used in a given round normally, and that the adjustments do NOT stack. This is why up above it says that the DB adjustments of the first have to be legal for the additional attacks as well. This way you aren't stacking the abilities of the specific maneuvers.
Personally, I would only allow the additional attacks to be used with a Basic Swing and nothing else, treating the Additional Attacks as if it were another type of Specific Maneuver (i.e. no more than one per round)....
