You are misinterpreting the rules. You need 250 hours of PIC. Your SIC counts towards the 1500 total time, but does not count towards the 250 PIC requirement unless you were acting as PIC and logged it as such...
(3)
Sec. 61.159 Aeronautical experience: Airplane Category rating.
(a) A person who is applying for an airline transport pilot certificate with an airplane category and class rating must have at least 1,500 hours of total time as a pilot that includes at least:
(1) 500 hours of cross-country flight time.
(2) 100 hours of night flight time.
(3) 75 hours of instrument flight time, in actual or simulated instrument conditions:
(i) An applicant may not receive credit for more than a total of 25 hours of simulated instrument time in a flight simulator or flight training device.
(ii) A maximum of 50 hours of training in a flight simulator or flight training device may be credited toward the instrument flight time requirements of paragraph (a)(3) if the training was accomplished in a course conducted by a training center certificated under part 142.
(4) 250 hours of flight time in an airplane as a pilot in command, or as second in command performing the duties and functions of a pilot in command while under the supervision of a pilot in command or any combination thereof, which includes at least:
(i) 100 hours of cross-country flight time ; and
(ii) 25 hours of night flight time.
(5) Not more than 100 hours of the total aeronautical experience requirements of paragraph (a) of this section may be obtained in a flight simulator or flight training device that represents an airplane, provided this aeronautical experience was obtained in an approved course conducted by a training center certificated under part 142.
(b) A person who has performed at least 20 night takeoffs and landings to a full stop may substitute each additional night takeoff and landing to a full stop for 1 hour of night flight time to satisfy the requirement of paragraph (a) however, not more than 25 hours of night flight time may be credited in this manner.