this is the only one of the five that reads something you were given rather than something you were born under. Your name was chosen, by someone, after you arrived. 姓名學 takes that choice seriously.
The method is arithmetic on brush strokes. Every Chinese character has a fixed number of strokes, and 姓名學 counts them the way the 康熙字典 did in 1716, which matters, because that dictionary counts a radical by its full classical form. 氵 counts as 水 (4 strokes, not 3). Use a modern count and every number below is wrong.
Those counts combine into five numbers, the five grids, and each is looked up in a table of 81 meanings that has not changed in centuries.
Three characters. Each carries a meaning and a stroke count, and it is the counts, not the meanings, that the arithmetic runs on.
Those three numbers are the entire input. Everything else in this chapter is arithmetic on them, which is why the next step shows the working rather than the result.
Five combinations of the same three counts. No lookups, no judgement. This is the part you can check with a pen.
Five numbers out of three counts. Now they get looked up, and this is where 姓名學 stops being arithmetic and starts being a tradition.
Each grid governs one area and carries one verdict from the 81-number table. Two of yours are 凶, inauspicious, and they are shown as plainly as the three that are not.
Read one at a time, that is five separate verdicts. But the grids also act on each other, and that relationship is the part almost nobody is shown.
Each grid carries an element, and elements act on each other, one feeds, one drains, one controls. 三才 reads those relationships rather than the grids alone. The map below shows what each grid does to you.
The grids are not simultaneous. Traditionally each governs a stretch of life, which is why an inauspicious number early and an auspicious one late is a very different story from the reverse.
Everything above, turned into something you can act on.