2. Definite sentences. A definite sentence of imprisonment commences when the prisoner is received in the institution named in the commitment. Where a person is under more than one definite sentence, the sentences shall be calculated as follows: (b) If the sentences run consecutively and are to be served in a single institution, the terms are added to arrive at an aggregate term and are satisfied by discharge of such aggregate term, or by service of two years imprisonment plus any term imposed for an offense committed while the person is under the sentences, whichever is less;
4. Good behavior time. Time allowances earned for good behavior, pursuant to the provisions of the correction law, shall be computed and applied as follows: (b) In the case of a person serving a definite sentence, the total of such allowances shall not exceed one-third of his term or aggregate term and the allowances shall be applied as a credit against such term.
N.Y. COR. LAW § 804
1. Every person confined in an institution serving a definite sentence of imprisonment may receive time allowances as discretionary reductions of the term of his sentence not to exceed in he aggregate one-third of the term imposed by the court. Such allowances may be granted for good behavior and efficient and willing performance of duties assigned or progress and achievement in an assigned treatment program, and may be withheld, forfeited or cancelled in whole or in part for bad behavior, violation of institutional rules or failure to perform properly in the duties or program assigned.
2. If a person is serving more than one sentence, the authorized allowances may be granted separately against the term of each sentence or, where consecutive sentences are involved, against he aggregate term. Allowances based upon sentences of less than one month may be granted, and in such case the maximum allowance shall be one day for every three days of the sentence. In no case, however, shall the total of all allowances granted to any such person exceed one-third of the time he would be required to serve, computed without regard to this section.