Making Infopath forms autonumber themselves

I am trying to make my infopath forms on sharepoint number themselves automaticly, i have used this guide to do this: http://ift.tt/16FEpot

I have gone through all the steps three times on three diffrent librarys but i get the same problem every time. When i try it out i can fill every field and it's all fine, untill i try saving it to the library. When i click save i get a warning telling me something is wrong and the form could not be saved. Thought when i click ''ok'' it actually gives itself the correct number. When shutting it down it even has saved into the library but without the ''autonumber''.

Does anyone have experience in autonumbering that can tell me what is wrong or maybe have a better solution?