Genre and place in the book. The spelling analogy: as a word is spelled out letter by letter — calmly and in order — so is any task. The principal discipline is action (the method: to carry a task through part by part); the sustaining one is assent (self-command, not to meet anger with anger).
The spelling analogy. "If someone asks how the name 'Antoninus' is spelled, will you strain (κατεντεινόμενος) to force out each letter? And if they grow angry — will you answer with anger (ἀντοργιῇ)? No — you will calmly (πρᾴως) reckon off the letters in turn." The name "Antoninus" is Marcus's own imperial name, a familiar example. (A play on words: στοιχεῖον means both "letter" and "element"; a word, like the cosmos, is composed of στοιχεῖα.)
Duty made of parts (καθῆκον ἐξ ἀριθμῶν). The moral: "every TERMduty (καθῆκον) is made up of certain parts (ἀριθμοί)." The same rare phrase stands at 03-01 ("the numbers of the appropriate," τοῦ καθήκοντος ἀριθμοί). Keep these parts and "carry through methodically (ὁδῷ) what is set before you." The task is done not in a rush but letter by letter: element after element, in order.
Without anger (μὴ ἀντιδυσχεραίνοντα). And — "without being disturbed (μὴ θορυβούμενον) and without returning annoyance to those annoyed (δυσχεραίνουσιν)." Another's irritation must neither knock you off your rhythm nor provoke annoyance in return: hold calmly to your task (cf. 06-06, 06-20 — not to become like, not to be hostile). Method and composure go together.
Disciplines and parallels. The principal one is action (the methodical completion of the parts); the secondary is assent (self-command). Parallels: 03-01 (τοῦ καθήκοντος ἀριθμοί); Med. 8.32 (divide the task into parts); 06-06, 06-20, 02-01 (without returning anger); 05-01, 06-02 ("the work of a human being," the fitting act).