Which number should be used as max_length restriction for instance_name field?

Current code doesn't have restriction on max_length for instance_name field in "update instance". When I did the test, I saw the backend seems to be using "255" as the max_length checking, as shown in the message below:

RESP BODY: {"badRequest": {"message": "Server name has more than 255 characters.", "code": 400}}

But current code in "create instance" does restrict the max_length for instance_name field, and it seems to be using "80" as the max_length restriction, as shown in the code below:

name = forms.CharField(max_length=80, label=_("Instance Name"))

So just would like to confirm which number should I use as the max_length to restrict the instance_name field in "update instance"? 80 or 255?

Thank you!