So let's assume a druid is wildshaping into something like a Dire Tiger, which has a claw damage of 2d4 and a bite attack of 2d6.
Now druid casts Strong Jaw on himself, counting the natural attacks as if it were 2 sizes larger.
That's easy for the bite as it's in the provided table (which only provides "normal" values for it's size, individual creatures can differ from it, which the Dire Tiger does, so just checking the value for gargantum creatures doesn't work) or also the Improved Natural Attack feat. 2d6 becomes 4d6.
However what happens to 2d4?
1d4 becomes first 1d6 and then 1d8 according to the list, so 2d4 becomes 2d8?
Once 2d4 becomes 2d6 it seems to follow the progression for 2d6.
So let's assume a druid is wildshaping into something like a Dire Tiger, which has a claw damage of 2d4 and a bite attack of 2d6.
Now druid casts Strong Jaw on himself, counting the natural attacks as if it were 2 sizes larger.
That's easy for the bite as it's in the provided table (which only provides "normal" values for it's size, individual creatures can differ from it, which the Dire Tiger does, so just checking the value for gargantum creatures doesn't work) or also the Improved Natural Attack feat. 2d6 becomes 4d6.
However what happens to 2d4?
1d4 becomes first 1d6 and then 1d8 according to the list, so 2d4 becomes 2d8?
The common rule is that every two steps the maximum damage is multiplied x2. Thus, the 2d4(max=8) will become 2d8(16) after two size steps. Had it been just one size, it would be multiplied x(3/2)--> 2d6(max=12).