This depends on whether you can prove that there is a factual labor relationship between the two parties; And submit sufficient evidence to support the arbitration request. Everything depends on the evidence.
"What should I pay attention to?"
My suggestions and reminders are as follows:
1. The part about unpaid wages. This part belongs to the unreasonable deduction of wages by the employer, and it can also claim 25% economic compensation, that is, 420+ 105, that is, 525 yuan. ("Punishment" without contract terms and clear rules and regulations is "deduction")
2. About overtime pay. Why the calculated number of days is 6 days should be explained in the documents applying for arbitration.
3. The part about double pay. Your calculation seems a little short. It should be 1200+ overtime+monthly supplementary meals 120 times the sum of 9 months.
Did your employer pay social insurance for you? If not, you can raise it.
In addition, I saw upstairs that "I advocate compensation equivalent to one month's salary", which is paid in lieu of notice; This cannot be advocated. Because you resigned voluntarily. I hope my colleagues don't take it amiss. )
I hope my answer is helpful to you. I would like to ask my colleagues to make corrections to help the questioner better.
Finally, shout a slogan: Long live the proletariat! Long live the working people! (hehe)