Actually even easier way:
Divide CALCULATED PAYLOAD by 95, and round down.
e.g.
Calculated payload 14,089 kg
Maximum payload 16,600 kg
% of maximum 84.9%
Fuel consumption 21,146 l
14,089 / 95 = 148.305 so this flight can take 148 pax.
If the actual assigned seating config has 155 pax (example) and 10 units of cargo, distributed in 130 Y and 25 C, it would make 123 Y pax and 25 C pax bookable in the ORS for that flight, with 0 units of cargo bookable.
CALCULATED: 148 PAX
Available: 148 PAX to be assigned
Assigned 25 to C
Remains available: 123 PAX
Assigned 123 to Y
Imagine same config but with 145 pax, and 10 units of cargo:
Distributed in 110 Y, 25 C, 10 F.
CALCULATED: 148 PAX
Available: 148 PAX to be assigned
Assigned 10 to F
Remains available: 138 PAX
Assigned 25 to C
Remains available: 113 PAX
Assigned 110 to Y
Remains available: 3 PAX
which is equal to 3x95 kg = 285 kg
Remains available: 285 kg
Assigned 2 units of cargo (2*100 kg)
edit: formatting and details