Reply To: Number lines (4 questions)
I think you'll get the best complete answers to your questions from NBA's Tactile Graphics Committee.
For what it's worth, if I were considering your questions for myself, I would take into consideration the following.
1. I know of no Tactile Graphic Guideline that says a graphic must be formatted according to Braille Formats 2016 or must be formatted beginning in cell 1. For all aspects of a transcription, I try to follow #3 of BANA's Provisional Guidance for Transcribing Mathematics in UEB, which includes the following:
Follow Braille Formats: Principles of Print-to-Braille Transcription, 2016 for the format of displayed literary text except for paragraph format, which is never blocked. For displayed mathematical expressions, use blank lines preceding and following; and indent 2 cells from the runover position of the material to which they apply.
Use of the full braille line for a displayed technical expression (with runovers in cell 3), is appropriate for higher math where expressions are lengthy and more complicated. The spaces used to indent beyond the runover in effect can make the difference between dividing or keeping a mathematical unit together.
2. A numeric passage seems to make a lot of sense for a number line. My team and I often use a numeric passage for number lines.
3. I know of no rule that specifies a number of horizontal line indicators between ticks and/or arrows in a number line. Tactile Graphic Guidelines6.5.1 does tell us, "Number lines are used to teach relationships between numbers; therefore, it is essential that the proportional spacing between units be preserved."
4. Conceivably, a number line can have a runover.