to re-download those 28mb because you already have that information in your mempool. With graphene you just send some information about what TXs are included in those 28mb. So you only
receive a packet of 0.5mb with Graphene. Do you see what I mean? In the end the blocksize ( written to HDD) will be 28mb, the TXs will have paid whatever fees they wanted, but this is
not what Graphene is about. Graphene help nodes communicate blocks faster because most of them have the same mempool of TXs. So you don't have to re-download all the TXs in the block.
Anyway I hope you understand this ELI5 I gave you. If not, please reply and I'll try it another way. All the best guy
