In this tutorial of Arpeggiator:
It is a bit hard to understand for me to figure out the actual use of “offset” value.
I have tried to modify the offset value from 0-1000, it seems no effect on the output sound.
For the argpeggiator, the offset is the position in samples from the beginning of the current audio block where the previous note is ended and the next note is started. You might not be able to hear much difference when changing this value if your audio block size (configured in the DAW or the Standalone audio settings page) is very small. For larger block sizes, you might hear the note timing become less accurate when assigning arbitrary values to the offset.
For the surround plugin, the sampleOffset is used to keep track of the phase of the output sine wave. Modifying the sample offset will just affect the (initial) phase of the wave, so you won’t be able to hear any difference in isolation.
very clear explanation, many thanks.