The TG Committee is currently reviewing the question and will post final response in the very near future. My apologies for the delay. It was an excellent question and we want to insure the information we provide is correct. Thanks in advance for your continued patience.
Thank you for the questions! Number Lines and Cartesian Coordinates are critical components of any STEM content and we wanted to make sure we had all the details covered. There are many intersecting rules and guidelines to consider and we hope the following addresses all of your needs. Please also see the attached document for an example.
A raised line drawing would be preferable if the readers' familiarity with braille graphics is unknown and required if the readers are K-3.
Alignment of numbers is with the first row of the digit rather than numeric symbol (GSTG 18.104.22.168).
Yes, the tics should be extended 1/4" (6mm) above and below the line itself if using a raised line drawing (GSTG, section 22.214.171.124).
Yes, put relevant symbols on SPECIAL SYMBOLS page per "Guidance for Transcription Using the Nemeth Code within UEB Contexts" item #17.
However, following GSTG 126.96.36.199 (second bullet) If number lines appear infrequently, the braille number line symbols should be inserted as a transcriber’s note. So, if this is the only place that a number line occurs, place the symbols in a TN immediately preceding the graphic.
Let us know if this answers all of your questions!