Hieroglyphs were used for different things! They weren’t always used to denote sounds, but sometimes whole words or parts of words. Some of the ways they were interpreted could seem like puns or puzzles today.
To make a very loose analogy, with emoji as hieroglyphs:
🦆 — can stand for a duck, the actual waterbird
🦆u — here, the sound duck is modified by another sign. This is the word duke.
🦆o — similarly, this is dock.
📐🦆 — by combining the signs for triangle and duck, we spell out the pronunciation of the word truck.
(🦒🦆🦒🦉📰) — the name Jack Jones, spelled as giraffe duck giraffe owl news.
This is an analogy; the point is that the same sign could be used for different things, especially at different times in history.