Receiving Walmart Moneygram?

I’m having a bit of trouble with receiving some money from a friend through the Walmart moneygram service. He lives in the U.S, and me in Canada. The reference number that he gave me was 8 digits long, and when I went to fill out the forms I was told it was supposed to be 10 digits. She tried anyway, and the order came up invalid. The only number that was 10 digits long was the PIN number and I also tried that one… not sure what’s going on here but I could use some help into how these things work. I’m certain that the numbers I have are correct, and that he actually sent the money. On the form it asked for a number but it wasn’t called reference or PIN… I forget exactly what it said, but it could have been hold number? Something like that.