IN, OUT, and the arrow between them

Eight connections, printed twice

Turn the module over and every connection it has is on the left edge, and again on the right. The left is under a label reading IN, the right under OUT, and between them a row of chevrons points from one to the other.

Which board this is. This is the newer board, the one with the PWM pad. The earlier version of this display had no dimming: five signal pins, no PWM row, and no way to change its brightness. Everything about the digit, the shift register and the chain is the same on both; the brightness pages are about this board only.

The two-hole row is the segment supply: GND and 12V. The six-hole row is everything else, top to bottom as the back prints it: GND, 3V3/5V, DATAIN (SER), LATCH (RCLK), CLOCK (SRCLK) and PWM.

The names in brackets are the shift register chip's own, which helps the first time you read a 74HC595 datasheet and find nothing called DATAIN. PWM is the sixth wire, and the one this board adds: the digit is dark unless something says otherwise, and chapter 4 is about what.

Only one hole changes meaning

Compare the two edges and they are the same list in the same order, with one exception. Where the IN edge says DATAIN (SER), the OUT edge says (QH) DATAOUT. That is the shift register's serial output, the pin that hands bits on to whatever comes next. TI writes it QH′ in the datasheet; the board prints QH. The latch and clock are printed with the chip's names first on the OUT edge, because there they are being passed on.

Everything else, ground, the logic rail, the latch, the clock, PWM and the 12 V, is the same copper on both edges. It goes straight across the board. That is why a chain needs one power supply and one set of wires from your microcontroller no matter how long it gets, and also why one PWM wire dims every module in it.

Neither edge has a header fitted. The holes are bare, and solder the headers first is about what goes in them.

Common anode, and why you can ignore that

Under the brand name the board says 4" COMMON ANODE 7-SEGMENT DISPLAY. Common anode means the display's LEDs share their positive side, and a segment lights when something pulls its other end down to ground.

In a circuit you built yourself that would invert every byte in your table. Here it does not, because the driver, U2, is an inverting low-side driver: it sinks a segment's current to GND when its input is high. So a 1 in the byte lights a segment, the same as it would on a common-cathode display. The silkscreen is telling you what the part is, not what your code has to do about it.

The ten pads that are not for you

Along the top edge: B, A, ANODE, F, G. Along the bottom: DP, C, D, E, ANODE. Those are the display's own pins, with nothing in front of them. The warning printed beside them is not decoration: there is no resistor between these pads and the display, and an LED with no current limit lasts about as long as it takes to notice.