Choice of resistor R8 R11

[ddieffen]

Hello,
I might misunderstand something but why R8 and R11 add up to 50.3k?
To my comprehension this would set the divisor to 5M/50.3k although it is possible to source a 3kOhms resistor for R11and make the ratio closer to 1/100 ?
Thanks

[lbarbisch]

You're correct, that would be a better fit.
I believe I did it like this, because that was what I had on hand at the time.
For a future version I would add trim pots to have the gain adjustable to trim out tolerances.