Server timeout setting is not reflected

Hello, I have two questions about WinSCP.

I set the server timeout setting to 15 seconds(default value).
But, actual time was 21 seconds(*1).
1. Why is the connection timeout set to 21 seconds even though it is set to 15 seconds?
2. What does mean "Timeout: 15sec" in logging message?

Logging Message:
. 2019-08-03 01:10:45.471 Ping type: Off, Ping interval: 30 sec; Timeout: 15 sec

1) . 2019-08-03 01:10:45.471 --------------------------------------------------------------------------
2) . 2019-08-03 01:10:45.471 Looking up host "xxx.xx.xx.xxx” for SSH connection
3) . 2019-08-03 01:10:45.471 Connecting to xxx.xx.xx.xxx port 22
4) . 2019-08-03 01:11:06.515 Failed to connect to xxx.xx.xx.xxx: Network error: Connection timed out
5) . 2019-08-03 01:11:06.515 Using non-standard protocol or port, tunnel or proxy, will not knock FTP port.
6) . 2019-08-03 09:01:44.546 --------------------------------------------------------------------------
(*1) connecting time from 2) to 5) is 21 seconds.

Best Regards,

Informations:
WinSCP version: 5.11.2
OS: 6.1.7601 Service Pack 1 - Windows 7 Professional
Transfer Protocol: SCP

The timeout is provided to OS API call. How OS handles the timeout is upon the OS. The timeout value is only advisory.

martin wrote:

The timeout is provided to OS API call. How OS handles the timeout is upon the OS. The timeout value is only advisory.

Dear martin
Thank you for early reply.

If the timeout setting value on Windows OS API is 21 seconds,
What value is set on WinSCP (for example, 100sec, 5sec), does it always time out at 21 sec?