Translation:The captain thinks that tomorrow is Wednesday.
My Even Shoshan lists only /kabarnit/, but the Academy now lists both - probably part of their lenience trend. I think, though I'm not sure (it's not a word that I hear too often...), that /kabarnit/ is more common in singular, and /kvarnitim/ in plural (especially in construct, /kvarnitey/). Possibly adding the syllable at the end increases the motivation to spare a vowel in the beginning.
As a Greek loanword, κυβερνήτης, the pronunciation would vary historically depending on the dialect of Aramaic that was influencing the niqqud, e.g., you can find the spelling קוברניטא and in Ester Rabbah 9b(12) קב[י]רניטין (source: Sokoloff, Dictionary of Jewish Palestinian Aramaic, 474). As Aramaic had a tremendous effect on Tannaitic and Amoraic Hebrew, the evidence for the Aramaic niqqud quḇernīṭ means that historically the initial vowel can probably be found in the history of the Hebrew language when Aramaic was used by Jews more than Hebrew in Hellenized contexts (so esp. in the amoraic period after the Bar Kokhba revolt). Pérez Fernández points the lexeme in rabbinic Hebrew as קְבֶרְנִיט, (p. 77), but he may be assuming its pronunciation based on the Greek. Most ancient texts do not have niqqud, of course. The modern Hebrew pronunciation is very interesting insofar as there seems to have been a deliberate effort to not pronounce the first vowel as u. In later Greek, that vowel would be pronounced as / i /, so Greek Jews who spoke/speak Greek mixed with Hebrew might pronounce it kibernitis. The Nazis tried to wipe out the Romaniote Jews. cf. https://en.wikipedia.org/wiki/Romaniote_Jews For a scholarly article: Steven Bowman, “Judeo-Greek” in Encyclopedia of Jews in the Islamic World (Brill, 2010). Online: https://www.jewishlanguages.org/judeo-greek Anyway, even though it's up to the people and Academy of Hebrew Language to decide how to pronounce it today, and you two have a better idea about that than I do, it's a mitzvah to remember Jewish pronunciations historically (mitzvah in the popular sense of a good dead).