Cyrillic rtsy writes the same consonant and takes the numeral one hundred, exactly as Glagolitic does. This is the first agreement between the two systems since the very first letter of the alphabet, and it is worth being clear that it is an accident of arithmetic. Cyrillic gets one hundred from Greek rho. Glagolitic gets it from counting nineteen letters. The two roads happen to arrive at the same place because the number of Slavic letters Cyrillic passed over in the first half of the order equals the number of Greek letters that stand between the two counts.
The agreement holds for the letters immediately following, through two hundred, three hundred, four hundred, five hundred, six hundred, and then breaks at the second o sign, where Glagolitic counts seven hundred and Cyrillic inherits eight hundred from Greek omega. After that Glagolitic stops numbering altogether while Cyrillic continues with two Greek letters and one Slavic affricate.
The names agree in sense, both being an imperative of the verb to say, and differ in form. The mnemonic sentence is the same in both traditions, and this is the letter at which most readers agree the sentence still makes plain sense.
Whether that sentence was composed as a text or emerged from a set of words chosen for their sounds is a separate question, and one on which the atlas takes no side. The first twenty names read as connected Slavonic and the rest do not, which is the fact everyone starts from; what is built on it varies. Reading the whole recitation as a devotional composition by the alphabet's maker is a position held in the literature, not a settled result, and it is recorded here as such.