Tina should have put it in more concrete terms. "Attack like you did a year ago" would have worked better. And "limit yourself to 100 castings, this target isn't as durable as in the mansion" would be even better.
But ultimately, it was a bad idea to keep the same-looking target and range while sneakily improving their capabilities. Now the MC will have to train a dozen chapters before he learns to scale his strength properly.