وَإِنِ ابْتَدَأَتْ مَعَ الْبُلُوغِ مُسْتَحَاضَةً: فَحَيْضُهَا عَشَرَةُ أَيَّامٍ مِنْ كُلِّ شَهْرٍ، وَالْبَاقِي اسْتِحَاضَةٌ.
Meaning: If a woman is experiencing istihadah from the onset of puberty, ten days of each month are treated as hayd and the remainder as istihadah.
This concerns a beginner with no established prior habit. Continuous bleeding cannot be classified wholly as hayd; Hanafi law assigns ten days as hayd and the rest as istihadah.