Dammatain ٌ- vowel sign consists of two components (1) Dammah ُ- that produces “ū” sound and (2) second Dammah, sign is an unwritten letter Nun Saakin نْ that produces “n” sound. Thus ﹴ will produce “in” sound.
Example بُنْ will be written as ﺑٌ will sound "Bun"

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