a cmbs issuance is $560,539,655, of which the aaa-rated senior tranches total $389,575,000 of the principal balance, the aaa rated subordinate class (or a-s class) is 28,727,000, the aa rated tranche is $15,415,000 and the single a rated tranche is $30,830,000. the amount of the deal that is subordinate to (also called the subordination level) the single a rated tranche is