Speex Adaptive Jitter Buffer get function

[Khubaib96]

Hi,
I have been working on the Speex adaptive jitter buffer. I am a little confused in understanding the specific get function:
int jitter_buffer_get(JitterBuffer *jitter, JitterBufferPacket *packet, spx_int32_t desired_span, spx_int32_t *start_offset);
*spx_int32_t start_offset parameter. I am attaching a snapshot. Could you please explain a little bit about this parameter?

Thank you!