Assalamualaikum wa rahmatullahi wa barakatuh
I have heard that first ilm ul qirat was written by ABU UBIAD AL QASIM (224 AH)
IBN JAZARI mentioned about the work of abu ubayd al qasim and said that in his (abu ubayd al qasim) work he mentioned 25 reciters i.e. 25 different recitations
Now my question is that today we have only 10 Qirats
What about remaining?

The statement of ibn jazari mentioned below

The most famous opinion among the scholars of al-Qira'at is that the first person to author in it was Abu 'Ubayd al-Qasim Ibn Sallam (d.224AH). Imam Ibn al-Jazari (d.833AH) said:

" فكان أول إمام معتبر جمع القراءات في كتاب أبو عبيد القاسم بن سلام وجعلهم فيما أحسب خمسة وعشرين قارئا مع هؤلاء السبعة"

"The first reliable Imam who compiled the Qira'at in a book was Abū 'Ubayd al-Qasim Ibn Sallam and mentioning within it twenty-five reciters which includes these seven"