You need to ask your friend what his dosage is or more specifically, how much Methadone he gave you. In the United States, Methadone is dispensed most commonly as a 10mg/ml solution. This solution is typically placed in a small bottle with a safety-seal, tamper-evident cap. However, no matter how much Methadone is given, the bottle itself will always be filled to the top with water. This means that everyone who leaves the clinic will be leaving with the same volume of liquid, but each bottle can contain a wide range of different dosages of Methadone.
There are people at the clinic taking 5mg per day and there are people who take 220mg per day. The only safe thing is to ask your friend. I'm surprised they didn't just tell you when they gave it to you. It just seems like a question that couldn't easily go unanswered during the conversation or handoff of the drugs.
At any rate, when you find out how much Methadone you have, I would shoot for 30mg Methadone to ease your symptoms and reduce by 5mg-10mg for up to 5 days. That would be pretty ideal in my opinion, but this will all depend upon how much you have and whether you can get more. Keep us posted.