HOLY SNARKLEROYS.
Haroun would ordinarily check at this point to see if Bella got the 『Light Magic』 Skill at Lv. 1, or maybe even higher. But if she can already cast spells just by hearing them or reading them, he's not sure how to check! Maybe see what she makes of the more advanced spells in his second-year 『Light Magic』 textbook -
Bella's later sentences catch up to Haroun's auditory processing.
"Tiring? Not unless you're low on mana, and you shouldn't get low on mana from just expending a tenth. I mean, it is a practice thing, and efficiency increases with Skill. But the average 12-year-old apprentice has around two units of mana before they start practicing at all, just from, you know, existing for 12 years - oh. Oh, dear."