Cyrillic kako writes the same consonant and takes the numeral twenty, against the forty of Glagolitic. Twenty is the value of Greek kappa, inherited straight across; forty is what Glagolitic reaches by counting its own letters from the first.
The two figures are now exactly a factor of two apart, which is a coincidence of where the skipped letters happen to fall rather than a rule, and it does not hold for long. The general point holds throughout: the Cyrillic number tells you which Greek letter occupies the slot, and the Glagolitic number tells you how far into its own alphabet the letter stands. The first is a fact about Greek and the second a fact about Slavonic.
Names and sounds agree in both scripts, as they do almost everywhere in the order. Kako is the same adverb in both recitations, and its place in the mnemonic sentence is the same.
The pair is also one of the places where the two scripts look least alike on the page. The Cyrillic letter is a Greek kappa with very little alteration. The Glagolitic letter is not, in either of its hands, and no proposed derivation of the Glagolitic shape from a Greek one has gained general acceptance.
The sound both letters record is one of the velars that soften in Slavonic before certain vowels, and both alphabets handle the softening the same way, by writing an entirely different letter rather than by marking the k. That shared solution is a further item on the list of things the two scripts agree about while agreeing about nothing visible.