Actually, I find this stuff interesting. Always a chance to learn through football about human interactions and dealings.
But there is no news about it coming from Brazil. The last I read was from Mundo Deportivo. Barça already paid 4 million euros for the priority rights and have until July 15th to pay the other 26 million euros. There´s no clause about antecipating the move to July, so Grêmio wants a compensation of 10 million euros, while Barça agrees to pay only 3 million euros.
Arthur moving earlier to Barcelona really hurts Grêmio´s chances to retain the Libertadores title, so there´s good reason to why they want a big compensation for it.