How do Rules 5 and 6 differ?

Miscellaneous Morphological Explanations: Eight Rules for Wāw, Yāʾ, Alif and Hamzah

• Both concern only jussive verbs
• 6 concerns masculine sound plurals
• 5 permits ḍamma/kasra cases; 6 gives two special fatḥa cases
• 5 applies only to final wāw