Growth discordance?

Princess 👶🏻👶🏻💖💙

I went to my last ultrasound today and in the results it says that there is 10th% growth discordance between my di/di twins. The tech did not look worried or anything but does anybody knows what that means? My boy is measuring a week a head and my girl is measuring 31w3d and I am 31w6d.