Based on those numbers, there is probably some sort of error in the measuring, or the readings.

Starting at 1.855, to 1.800 the load changes 15lbs in .055”. Then 30lbs in the next .065”, then 20lbs in the next .065”, then 50lbs in the next .130”(25lbs per .065”).
The spring rate between those data points vary greatly........
272.7
461.5
307.6
384.6

If you compare the rate for each lift point against the 1.855 starting point......
272.7
375.0
351.3
365.0

You are using a retainer when checking the springs, right?

I’d probably shoot for 1.825”(assuming a net lift of .568” like posted earlier).