inputQueueSize metric

[rania duni]

Regarding the inputQueueSize metric. What does it express after all?
Observing the inputQueueSize and inPoolUsage metrics in Prometheus,
 I found that when the inPoolUsage is high, the inputQueueSize is low.
Thisobservation does not match the description of the inputQueueSize.
Therefore, does this metric express the size of the input buffers of
each task, or
does it express how full the input buffers of a task are?
Thank you in advance.