You are correct, ARD is not a conviction. So you have answered the question correctly. Since the employer can read the same information, be prepared to answer questions about it truthfully.
I do not know where Government-Records.com gets its information. I understand that the State Police records can be expunged (showing the records of arrest and subsequent proceedings), but you must make a specific request, probably in writing. This may be the source of the report you read. It is also possible that the information was picked by Government-Records.com while you were still on ARD.
Unfortunately, no matter what the County does, Government-records.com is not going to expunge the information it has collected. It is on their data base and is going to be available to paying customers for as long as that organization exists.
Good luck with the job interview. Don't assume that they will disqualify you. They may accept your explanation.
The ARD only means that your case was dismissed and expunged; your case does not count as a conviction because you didn't plead guilty and therefore weren't convicted.
First, you should check with an attorney that handles expungements in and around the county where you completed your ARD program. You should also check with that county's Clerk of Courts. Most of the expungements that I handle are in Allegheny County. After the Court of Common Pleas Judge, who is assigned to Motions Court, signs the expungement Court Order, the Clerk of Courts sends it to various agencies to "clean up" the records of the incident. It does take some time for all of these agencies to remove these records, but I highly doubt that a copy of the Order was sent to Government-Records. You may want to contact Government-Records and tell them to remove all records regarding your case.
Second, you should consult with an employment lawyer. With ARD, you did not plead guilty and were not convicted; you only agreed to enter the ARD program and follow the terms and conditions of the program. You completed ARD, and the case was dismissed and expunged. But an employer may also find this information that you found on Government-Records and not hire you. If that happened, you should absolutely see an attorney who practices employment law.