The above figure of ~ 64 million speaker is given for Egyptian Arabic.
The Wikipedia page shows the same number of ~ 64 million speakers of Egyptian Arabic but it also says that Egyptian Arabic and Masri are the same.
I did find however a page where they talk about the different Egyptian Arabic dialects of which Masri is one of them.
- Masri: This is the most widely-spoken Arabic dialect, and is spoken mainly by the inhabitants of Egypt’s capital city, Cairo, and the surrounding cities. This dialect was derived from the spoken Arabic form that came to Egypt with Islam and was later influenced by the local Coptic language and other foreign languages such as Italian, Turkish, English and French.
- Saidi: This is the dialect spoken by Saidi people who live in Southern Egypt near the Sudan border. It differs slightly in the cities along the Nile and gets more complicated farther south, where it has some similarities with Sudanese Arabic.
- Bedawi: This is the dialect spoken by the Bedouins in the Sinai Peninsula and the eastern parts of Egypt. It is also spoken in neighboring countries like Syria, Jordan, Palestine and Saudi Arabia. Bedawi is made up of several dialects including Levantine Bedawi Arabic and Eastern Egyptian Bedawi Arabic.
https://www.globalizationpartners.com/2017/05/31/egypts-spoken-arabic-dialects/
It could be possible that they thought that Masri was the same as Egyptian Arabic, even though it is a sub-dialect. It could also be possible that the figure of ~ 64 million speakers only counts for the Masri sub-dialect of Egyptian Arabic, but not for the Saidi and Bedawi sub-dialects.
I think if you would add up the number of speakers of the Masri, Saidi and Bedawi sub-dialects together, you would come to a figure of 100 million, in other words, the whole population of Egypt.
