Praise be to Allah.
It is not valid to ascribe reward and virtue to this du‘aa’ or to any other du‘aa’, dhikr or act of worship without sound evidence from the Qur’an and Sunnah.
The report mentioned in the question is not narrated in the books of the scholars, and was not narrated by the scholars of hadith in any of their books. Therefore it is not permissible to spread it among people or to speak of it, except by way of warning against it. What is required of the Muslim is to beware of spreading lies about religion. Whoever is heedless concerning that will be subject to a share of the supplication of the Prophet (blessings and peace of Allah be upon him) against those who tell lies about him deliberately.
Shaykh Ibn ‘Uthaymeen (may Allah have mercy on him) was asked the following question:
How sound is the du‘aa’ of a woman who says “Laa ilaaha ill-Allah ‘adada ma kaana wa ‘adada maa yakoonu, wa ‘adada harakaatihi wa ‘adada khalqihi min khalqi Adam hatta yub‘athoon (There is no god but Allah, the number of all that was, and the number of all that will be, and the number of their movements, and the number of His creation from the creation of Adam until they are resurrected)?
This type of du‘aa’ is too verbose. If she were to say: Subhaan Allah wa bihamdihi ‘adada khalqihi (Glory and praise be to Allah, the number of His creation), or Laa ilaaha ill-Allah ‘adada khalqihi (There is no god but Allah, the number of His creation), that would suffice and there would be no need for all of that. One of the dhikrs of the Prophet (blessings and peace of Allah be upon him) was: “Subhaan Allaah wa bi hamdih, ‘adada khalqihi; Subhaan Allaah wa bi hamdihi ridaa nafsihi; Subhaan Allaah wa bi hamdihi zinata ‘arshihi; Subhaan Allaah wa bi hamdihi midaada kalimaatihi (Glory and praise be to Allah, as much as the number of His creation; Glory and praise be to Allah, as much as pleases Him; Glory and praise be to Allah, as much as the weight of His Throne; Glory and praise be to Allah, as much as the ink of His words).”
This is one of the most concise of tasbeehs. As for these things that some people say, impressed by the rhyme and the invented meanings, turning away from that and focusing on what is narrated in the Sunnah is the best approach. End quote.
Liqaa’aat al-Baab al-Maftooh (no. 63, question no. 14).
And Allah knows best.