Cuadros literally translates to "squares" or "paintings". However, in the context of this song and the corrido tumbado genre, it's a slang term for bricks of drugs, likely due to their rectangular shape.
The lyrics "Los cuadros libretas se van por mar" (The notebook squares go by sea) use this double meaning to talk about trafficking. Understanding this key piece of slang is essential to unlocking the real story behind the song and its title.
Peso Pluma kicks off this track by telling us to sit down and listen to a true story: "Siéntense porque les voy a contar / Unos relatos que a mí me pasaron" (Sit down because I'm going to tell you / Some stories that happened to me). The story is about his rise in a dangerous but profitable business. He boasts about his success from the very beginning, saying "Cuando yo empecé me fue muy bien / Ahora me ven gastar al cien" (When I started, it went very well for me / Now they see me spending 100%).
The whole song is a pretty direct description of his work. He talks about supplying clients monthly and having bodyguards because "No vaya a ser que por ahí ande el diablo" (Lest the devil be around). The chorus is all about the logistics of his operation, moving packages, "Los cuadros libretas se van" (The notebook squares go), by sea while avoiding the authorities, or "Marinos por el altamar" (Marines on the high seas). It's a classic corrido theme: a narrative of a risky lifestyle, told with a calm, matter-of-fact confidence.