I am giving you the example in imperial. you may working in metric but the process is same.
First of all, In which specification you are working is need to know, like I am using a specification (Pressure class) as +3"WG and my standard length is 60 in this specification class.
So, need to know what is the standard length mentioned in your specification. from here,
You can check & change standard length from by double clicking the condition here, you can set 3000 to 4000.

But make sure you have setting it for All Type / Straight Piece not fitting (See "valid for" option in 1st snap)
But if you don't need to change core database and want to locally update your standard length locally for few times we can go to content icon >> Right click >> Edit >> and change standard length from "Auto" to Value as 4000. In my case it is 120.

Thanks,
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