The reason why the invoice for dinner in Beijing is from Hunan may be due to the following:

1. The restaurant is registered in Hunan, and even if it has a branch in Beijing, it will still use the invoice from Hunan to issue the invoice.

2. Tax policy and financial management needs, the restaurant chose to invoice in Hunan, which is not directly related to its business region.

Please note that the specific reasons also need to be determined according to the actual situation and the relevant tax policies, if in doubt, you can consult the relevant tax authorities or restaurants.