Thank you for the question, Melissa.
We know that 6.5.1.1 in the Guidelines and Standards for Tactile Graphic Guidelines tells us, “A numeric indicator is not used before a number if it occurs below the number line, whether the number is whole, fractional, decimal, or negative. …”
Please let me check with some colleagues before I tell you for sure how to transcribe digital time labels below a number line.
–Kyle