وَمَنْ تَسَحَّرَ وَهُوَ يَظُنُّ أَنَّ الْفَجْرَ لَمْ يَطْلُعْ
Translation: Whoever ate suhur while thinking that dawn had not yet appeared.
“Tasahhara” means taking the predawn meal. The person intends to fast but mistakenly thinks night remains. The fact later established is that true dawn had already begun while they ate.
The decisive problem is not a late meal as such: the food was actually consumed after the start of fasting time.