Question About PayPal Invoice

[Rue1e]

Hello guys i have a question about invoice since recently i've got myself for first time into online trading (You give goods - they send you money) 

I got the customer that send me a Paypal Digital Gift Invoice i dont know if its real or not since its been 24 hour and i still dont get my money 

So my question is is it real if its real how long it take for money to get on my paypal account 

If its not real or if its refundable please let me know so i can cancle the shippment thx ahead