anyone who can explain more on the difference between segment.abs_rate and segment.abs_applied_rate

[bcxa sz]

Hi Developers,

I am reading the design document on the sync and notice formulas to
calculate the running time and the stream time:

B.running_time = (B.time_stamp - NS.start) / NS.abs_rate + NS.accum

stream_time =  (B.time_stamp - NS.start) / NS.abs_applied_rate + NS.accum

Anyone can explain to me why the running_time use abs_rate but
stream_time use abs_applied_rate?