Value for tGuessSd for determination of Temporal Order Threshold (TOT)

Hi PTB experts!

In my experiment I am measuring the (Visual) Temporal Order Threshold.

I use QuestMean as algorithm for the determination of the TOT (40 Trials).

Does anyone know which value I should use for tGuessSd (estimated standard deviation for the Order Threshold)?

For example:

If I use a small value for tGuessSd (for example 10ms) then the algorithm(QuestMean) is doing smaller steps (up and down) as if I would use a bigger value (e.g. 20ms).
Let's say I have an estimated Order Threshold (tGuess) of 20 ms(determined by the subjects former trials), then the question would be how big I should set tGuessSd; e.g. 2m, 10ms or 20ms...). I am not sure if I should keep the value for the estimated standard deviation as narrow as possible or not.

Does anyone have an idea for that?

Thanks and all the best,

Armin