If I'm reading things right, a concentration check is based on you CON, if I take 36 points damage from a single hit, the DC to maintain concentration would be 18.
I would have to roll a concentration CHECK, my CON is 16, that gives me a plus 3. I roll a 14 + 3 = 17, that would be a fail, but since my Bladesong is active, I get to add my INT bonus.
My INT is 14, that gives me a plus 2, so my concentration check roll would be the 14 + 3 + 2 = 19, I made my concentration check then.
The coding would be "CHECK:[CON],+2, concentration"
The coding can be a little confusing, when things are not shown "(c)"