FYI
This weekend had new "RHS-10ATC" setting "verified" against the "master" refractometer used by the Seattle Aquarium ("special job", not a service normally provided the public -

- found the right guy to do for me, which he did, as long as I never told anyone...so forget all of the above after reading...

)
The "default setting" it came with was perfect. No adjustment necessary...
OmarD
(I did not say this...)