The poem is a short, puzzling confession about a way of seeing that falls short of what's expected. The speaker says "clock-talk" is what they ought to learn, which suggests a skill that belongs to the grown-up, practical world of schedules and telling time. But they're "one-eyed," and with only one eye the world loses depth. That fits the title: everything looks two-dimensional, so what they can grasp is lines, flat marks and edges, rather than the fuller picture.
The last two lines turn oddly tender. The speaker has learned "how to like / a great wrong card," as if taking pleasure in something that doesn't fit or doesn't win. Judging by the imagery, the card could be a misdealt hand or a misprinted picture, though the poem never says which.
The mood is wry and quietly self-accepting. There's a little embarrassment about falling short, but also a shrug, and even affection for mistakes and limited ways of seeing.