You can use fixed point arithmatics. Assuming every unit represents 0.01:
T = 2557 - 1249*A/100000
(Make sure that you multiply by A first before dividing by 100000)
The resulting value T is x 100.
You can store value of T in timer #1 S.V using SETTIMERSV.
You can store it in timer #1 P.V (present value using TIMERPV[1] = T.
If you define timer #1 as High speed timer then each unit of T represent 0.01s.