I don't think this has been documented, but was discussed in another thread, but it's not a case of writing text into a dial. It allows you to enter amount with units, so rather than having to enter a number between -64 and 64, you can enter the values that get shown to the left, e.g.
For an envelope attack, you can enter 3ms, rather than -60.15.
For an envelope decay, you can enter 1s, rather than 53.28.
For an LFO, you can enter 5hz, rather than -0.51.
For an oscillator, you can enter 2khz instead of 31.21, or C#5 instead of 9.00, or x2 instead of 12.00.
Hopefully this makes a little more sense, now?