Google Chrome devtool : Issue with started at & queued at timing

In chrome 1st request Queued at 0.0 ms and stared at 1 ms but
2nd immediate request queued at 15 s and stared at 10 s. not able to understand why 2nd request start at 10 and Queued at 15 senter image description here where is 5 sec missing. plz help