جَلَسْتُ جَلْسَاتٍ
Translation: I sat several times.
جَلَسْتُ: past verb with attached subject.
جَلْسَاتٍ: accusative absolute object; sound feminine plural, so its accusative sign is kasra.
Important: despite being accusative, “jalasātin” takes kasra as the accusative marker of the sound feminine plural.