Verse 28

لِّيَعْلَمَ أَن قَدْ أَبْلَغُوا۟ رِسَـٰلَـٰتِ رَبِّهِمْ وَأَحَاطَ بِمَا لَدَيْهِمْ وَأَحْصَىٰ كُلَّ شَىْءٍ عَدَدًۢا

This is in order for Him to know that they have delivered all their Lord’s messages and He fully encompasses everything they do and He has assigned a number to everything.