What does the numerator and denominator fields mean on the clock configuration screen of the MPEG Player tool?

What does the numerator and denominator fields mean on the clock configuration screen of the MPEG Player tool?

The numerator and denominator on the clock screen are essentially meaningless. They represent two hardware registers within the instrument that are used to calculate the output bit rate but the formula you see on that screen "A/B*27" is the extend of their meaning. Generally they are ignored and the desired bit rate is entered into the bit rate field instead, leaving the software to calculate the values of those two registers on its own.

The clock screen is covered in more detail on pages 3-8 and 3-9 of the MTX100A user manual.