I'm sure Matthew will be fine. There will be times when he doesn't drink all of his formula for one reason or another (ie he's sick, he fell asleep before he could, etc). Try not to stress about it and just know that tomorrow will be another day, and you can try again then.
Obviously completely refusing to drink his formula isn't good, but if he's just missing his last cup every once in awhile it shouldn't be a problem. If you're worried about it you could try giving Matthew an extra ounce of formula in each bottle or giving him one of his bottles earlier than you normally do.
Will you guys be at the May cooking class? I cannot make it, but I know my Mom will be there with my sisters Erica, Faith, Genavieve, and my brother Brennan.