That's a promotion? That sounds more like a regular department transfer to me. A promotion is when you're made a department head or backup department head.
Sounds crappy that day grocery would have a higher pay than GM. They're both pretty similar jobs. You receive the product, stock the shelves, and run your backstock. And you have to remember that neither of these departments have to deal with a cooler/freezer (dairy, frozen, produce, nutrition, deli, meat, bakery), neither of them create product (deli, meat, bakery, floral, produce), and neither of them really have to do any rotating (dairy, frozen, produce, nutrition, deli, meat, bakery). And what's ****ing hilarious about all this is that both of these departments are the easiest to get full time in and have the most freedom. But somehow a transfer from one easy dept to another warrants a raise? Either you're working 3rds or your raise is imaginary.