I certainly wouldn’t base a decision on if it is an FP on only 30% detected something, it is a little more complex than that.
With 4 of the 10 detections being heuristic or generic, leaving 6 detected by signature so it is certainly suspect and I would suggest it should be sent to avast for analysis, see below.
Are you getting any strange symptoms , e.g. what made you do an anti-rootkit scan ?
Send the sample to virus@avast.com zipped and password protected with the password in email body, a link to this topic might help and possible undetected malware in the subject.
Or you can also add the file to the User Files (File, Add) section of the avast chest (if it isn’t already there) where it can do no harm and send it from there (select the file, right click, email to Alwil Software). No need to zip and PW protect when the sample is sent from chest. A copy of the file/s will remain in the original location, so any further action you take can remove that.
They usually do not send it, I mean, there isn’t an automated system (robot) to answer.
They usually answer by correcting the detection in the virus database.