Assalamu alaykum wa rahmatullahi wa barakatuhu.
I got talaq from my husband on the 8th of September 2018. And then I got my first haiz on 11th September 2018 and second haiz on 6th October 2018. Till how many days is my iddat? From March 2018 I have not been living with my husband and talaq happened in September. So should I be waiting for 3 months 13 days in total or go according to the haiz date? An important thing to mention is that I am of the Shafii Maslak so please answer accordingly.
بِسْمِ اللهِ الرَّحْمنِ الرَّحِيْم
In the name of Allah, the Most Gracious, the Most Merciful
Waiting periods (‘Iddah) are of three types. The first one is the waiting period of the living, which is three aqraa, if the divorcee is a free woman who undergoes her monthly menstruation cycles, or three months in the case of a divorcee who doesn’t undergo monthly menstruation cycles. It is known from the speech of the Arab that the word qur’ means to seize/to stop, as one would say: “he has stopped the water in his pond”. Likewise, in the period of a woman’s purity, the blood seizes. Therefore, qur’, is the period of a woman’s purity in between her menstruation cycles. Allah Ta’ala has ordered divorcees that they wait for three aqraa (plural of qur’) when they are divorced by their husbands as He says in the Noble Qur’an: “Divorced women remain in waiting for three periods…” After this waiting period, they become free from the bond of marriage.
Based on the detail you have provided regarding your menstruation (haidh) and purity (tuhr) periods, when you get your November haidh, two purity periods (at’haar) will be over, and as soon as you get your first day of your December haidh, three full purity periods (at’haar) will be over and your ‘iddah will be complete.
Only Allah knows best
Written by Alimah Sabrina al-Faarsiyyah
Checked and approved by Mufti Mohammed Tosir Miah
Darul Ifta Birmingham
 Al-lubaab fil Fiqhi ash-Shafi’ee 1/340, Dar al-Bukhaari
أحدها: عدة الحياة، وهي ثلاثة أقراء٤ أو ثلاثة أشهر٥ في الحرائر (٤ إن كانت حرة ذات قُرء.)
 At-Tadreeb fil Fiqhi ash-Shafi’ee 3/398-399, Dar al-Qiblatain
وقال الشافعيُّ: القرْءُ اسمٌ وُضِعَ لِمعنًى، ومعروفٌ مِن لِسانِ العَربِ: أنَّ القَرْءَ الحَبْسُ، تقولُ العربُ: "هو يَقرِي المَاءَ فِي حَوضِه"، وفِي الطُّهرِ: دمٌ يُحْبَسُ. فالقُرْءُ: هو الطُّهرُ، والأقراءُ الأطْهَار
 al-Qur’an 2:228