Matthew was drawing large currents of mana into his core to saturate it to the point of there not being anymore space inside it. It didn't take him long due to the amount of mana that he already had stored. If someone looked inside his core at the moment, what they would find was a swirling mass of purple mana that looked vaguely like a small hurricane.

The next step he had to take was to push the walls of his mana core to the point that it expanded to the normal grade. This was the hardest part as his reinforced core was very sturdy and might develop cracks if he expanded it too fast. Cracking his core at this point would take him days to fix even with his enhanced recovery and the amount of mana he would have to use to do so would equal the amount he needed to expand his core by several fold.

It took him a little over a full day in the training room to reach the threshold of the normal grade core. All he need was a small push with a little more mana that he had to