[Blindmath] Nemeth Code Questions

[ALLEN PURVIN]

Hi,
I have Nemeth Code questions concerning Rule XIII  § 78.  I am using the 1972 Revision. In my book, this section appears on pages 88-89. My questions concern Nemeth commas used in superscripts or subscripts.
1. Why cant you use a Dot 6? Why must you use Dots 2-4-6?
2. In examples 2 and 3 on page 89, the first example says there is a space after the comma and the second says there is no space after the comma, but I can’t tell the difference. I was wondering if someone could explain the difference to me.
For those without access to the manual I will try to explain what I am talking about. Sorry for the confusion.
Example 1:
X with a subscript  of open parenthesis a comma b close parenthesis . 
The comma is not followed by a space in the ink print.
In Braille it is coded as X, subscript indicator, open parenthesis, a, Dots 2-4-6, b, close parenthesis.
Example 2:
X with a subscript of 1 comma 2. 
The comma is followed by a  space in the ink print.
In Braille it is coded as X, subscript indicator, 1, Dots 2-4-6, 2

Thanks!
Sorry again for the confusion.
- allen
(who is trying to get his Nemeth correct for Common Core Geometry)