The DR number, Diederich Rank, refers to the highest number in Diederich's frequency listing, which you can see here: Diederich Ranking.
DR 6. id est = i.e. ~ Note: Compare the English expression, "that is" or "that is to say." The Latin phrase is used to indicate when you are restating something in different terms.
DR 7. Quod sumus, hoc eritis. ~ Note: Guess where you find this expression...? Carved on a tombstone, alerting passers-by to their certain fate!
DR 10. ad hoc ~ Note: We use this Latin phrase in English to mean something invented or adapted for a particular moment or occasion. For more information, see the Wikipedia article.
DR 16. Quod dixi, dixi. ~ Note: As often, the antecedent of the relative pronoun is not expressed: (Hoc), quod dixi, dixi. This is a motto of the Dixon family (note the nice play on words: Dixon-dixi), echoing the famous words of Pontius Pilate, "Quod scripsi, scripsi" in the Gospel of John, 19.
DR 20. Ipse dixit. ~ Note: This refers to something which is meant to be accepted on the authority of the speaker, ipse, alone. Cicero, in his treatise De Natura Deorum, 5, refers to the students of Pythagoras in this regard: Nec vero probare soleo id, quod de Pythagoreis accepimus, quos ferunt, si quid adfirmarent in disputando, cum ex iis quaereretur, quare ita esset, respondere solitos "ipse dixit." This is one of the sayings Erasmus included in his Adagia, 2.5.87.
DR 23. Non omnia possumus omnes. ~ Note: You can find this saying in Vergil, Eclogue 8. This is also one of the sayings Erasmus included in his Adagia, 2.3.94.
DR 24. de facto ~ Note: This is a Latin expression sometimes used in English to mean something like "for all intents and purposes" or "in fact," even if it is not something officially established. Read more at this Wikipedia article.
DR 24. Dictum, factum. ~ Note: This little two-word saying is a great example of how succinct a Latin proverb can be. In English we would say "(no sooner) said (than) done." Compare the saying in the Adagia of Erasmus, 3.6.85: Dictum ac factum.
DR 24. Fac, si facis. ~ Note: You can find this saying invoked in Martial's Epigrams, 1.46.
DR 24. ipso facto ~ Note: This Latin phrase, used in English, refers to something that has happened as a result of some specific action itself, "in and of itself" (that is, in and of that action). For more information, see this Wikipedia article.