Looking for an Engineer or Math Teacher

I have a pneumatic system with a tank and air bag with 2 pressure transducers/sensors.
The air bag can be deflated/inflated using a solenoid valve.
Pressure sensors values are in 2^10 (from 0 to 1023)


Calibration / Data I know:
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going from: 108 min sensor reading
to: 540 max sensor reading
with: 603 max sensor reading in tank
takes: 3.86 seconds
(108-540 is the air bag max deflate/inflate range and 603 is tank max value set)

To be kept in mind: the smaller the sensor reading in tank, the slower going from 108 to 540 will be. 
So this is another example to depict this:

going from: 108 min sensor reading
to: 540 max sensor reading
with: 590 max sensor reading in tank
takes: 4.12 seconds


My problem:
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I need to find out the following real-life use-case:

going from: 200 current sensor reading
to: 300 a previously preset sensor reading/value
with: 568 current sensor reading in tank
takes: X seconds

Need to find out the X (seconds).


Let me know if anyone can help, thank you!
Marius