Increasing mutual fund "Fraction Traded" seems non-functional

[Jeff Kletsky]

I am working through some mutual fund transactions and, under 2.4.0, XML 
backend, it seems as though it isn't possible to increase the precision 
to match that of the statements, once it is established.

* Enter data (from OFX) into mutual funds created with the "generic" 
four-digit precision
* Note that the required precision is six digits
* Use the Tools > Security Editor to change the "Fraction Traded" to 
1/1000000 (six digits)
* Go to the account and note that things are still getting rounded to 
four digits
* Close GNUCash and reopen
* Go to the account and note that things are still getting rounded to 
four digits
* Confirm that the Security Editor indicates six digits

It's been a long day of lots of little numbers. Anything I'm missing 
with GNUCash?

TIA,

Jeff