[O] org-calc-default-modes not found!

[AW]

Dear list!

org-version: Org mode version 9.1.9 (9.1.9-8-gf05c2e-elpa @ .../.emacs.d/elpa/
org-20180409/)

[I shortened the path]

C-h v org-calc TAB

results in [No match]

Expected result: find variable org-calc-default-modes

But I'd like to set (float 8) to (float 16) in orgtbl-mode tables, because 
when I export them to LaTex, in my case I get some rounding errors I'd like to 
avoid. 

However, I'm really concerned about the fact that the whole variable isn't 
found.

org-table.el is there and it contains the variable. I loaded org-mode via 

(add-to-list 'package-archives
 '("org" . "https://orgmode.org/elpa/";) t)

No other org-mode around, as far as I can see. 

For testing  I inserted into my .emacs under custom-set-variables these lines:

'(org-calc-default-modes
   (quote
    (calc-internal-prec 12 calc-float-format
                        (float 16)
                        calc-angle-mode deg calc-prefer-frac nil 
calc-symbolic-mode nil 
calc-date-format
                        (YYYY "-" MM "-" DD " " Www
                              (" " hh ":" mm))
                        calc-display-working-message t)))

As far as I can see, the calculation is correct, Example:

| 105000200.77 |
| 105000400.05 |
|--------------|
| 210000600.82 |
#+TBLFM: @address@hidden@2$1

But why is the variable not found?

Regards,

Alexander