Hi Osman … the lack of accuracy on the example is due to nature of HLS. When you seek in HLS, it will start on a segment, not the middle of it (video needs to start with a full Key frame). In this example, the segments are 10 secs, which you can see on the manifest definition. So, any jump in video will be on a 10sec factor.
You can modify that for sure when you control the content, either coming out of a streaming server or a static delivery (like this example) … you can’t control that from the player side.
Be careful modifying the duration of chunks as it will have effect on the streaming experience. The latency for downloading a chunk is important. Most player follow the HLS draft to keep in memory no more than 2+1 chunks of buffering content.
regards