What a 65% board keeps and drops
A 65 percent keyboard drops the function row and the navigation cluster but keeps the arrow keys and a narrow right-hand column, usually Delete, Home, Page Up and Page Down. It is roughly 67 to 68 keys depending on the model, and it is the smallest layout that still has dedicated arrows.
Because the exact right-hand column varies between manufacturers, the board drawn here is the common arrangement rather than a specific product. If your keyboard puts different keys in that column, test them anyway: the readout below the board names whatever key you actually pressed, even when this layout does not draw it.
The function row is a layer, not a row
There is no F1 to F12 on a 65 percent board. Those keys live on a layer, reached by holding Fn and pressing the number row. Whether the browser sees F1 or the digit 1 depends on the keyboard firmware, and that is genuinely useful to know: if holding Fn and pressing 1 shows F1 in the readout, your layer works and any software that wants F1 will get it.
If nothing changes when you hold Fn, that is expected. Fn is almost always handled inside the keyboard controller and never reaches the operating system at all, let alone the browser.
Testing a board you just built
A freshly built or freshly flashed 65 percent board is the most common reason to run a test like this. Work along each row in order and watch the untested count fall, rather than mashing keys, because a missed key in a hand-soldered build is exactly what you are looking for.
A key that reports the wrong legend is a firmware mapping problem rather than a hardware fault. The readout shows the code the browser received, which is what you need to compare against your keymap.