The starting ayah of some juz can be different depending on the Quran script or Mushaf you are using. 

For example, in the Uthmanic script, Juz 23 starts from Surah Ya Sin ayah 28, but in Indopak script, it starts from ayah 22. 

To know the differences between Uthmanic and Indopak script, check this faq.

Here are other differences you might see:

• Juz 4: Surah Ali-‘Imran ayah 92 or 93
• Juz 7: Surah Al-Ma’idah ayah 82 or 83
• Juz 11: Surah At-Taubah ayah 93 or 94
• Juz 14: Surah Al-Hijr ayah 1 or 2
• Juz 20: Surah An-Naml ayah 56 or 60
• Juz 21: Surah Al-‘Ankabut ayah 45 or 46
• Juz 23: Surah Ya Sin ayah 22 or 28

Our app uses the most commonly referenced Mushaf for each script. Whether you use the Uthmanic or Indopak script, the Quran is the same, and these differences do not affect the recitation or meaning.