Feminine third-person forms refer to one woman, two women or a group of women. Their suffixes show both gender and number.
TypeFirst formSecond form
Singularفَعَلَتْ: she did.فُعِلَتْ: she was acted upon.
Dualفَعَلَتَا: the two women did.فُعِلَتَا: they two were acted upon.
Pluralفَعَلْنَ: the women did.فُعِلْنَ: they were acted upon.
Here ـتْ marks feminine singular, ـتَا feminine dual, and ـنَ feminine plural. In particular, فَعَلْنَ is not the masculine plural فَعَلُوا.