You get one drop per level of chest. A level 9 chest is 9 drops, each random and each multiplied by the room multiplier and rounded after each step (any ingot @ 2.45 = 2 ingots, any ingot @ 2.5 = 3 ingots etc, rounded then doubled for hoard quality 8+). The chest open animation always resolves exactly 4 things shown, showing by unique types of item gained, and if it runs out of unique types it repeats indiscriminately regardless of how many “drops” you got of a given item. If you had a 2.x modifier with Hoard Quality 10 that resolved as 4 ingots, you had a < 2.5 modifier (and if this was in Hall of Guardians, it means you either didn’t completely clear it, or you picked the 0.5 modifier start option) your 9 drops were 1 mythic ingot and, most likely, 8 drops of various shard amounts resulting in 4 mythic ingots and 50-100 shards total. Your chest open animation before the rewards screen would have shown 2 shards and 2 ingots, because only two unique types of thing were in your reward.
If the faction you are at hoard quality 9 is regularly receiving groups of 8/16 ingots, you are most likely still progressing the level on this delve choosing the rightmost option, starting at 2.0 modifier and ending at 3.5+. Which would result in a single ingot drop being resolved to 8. As soon as you wall out and can’t do full clears anymore in this delve, or worse, start taking the leftmost “lower level” delve option to be able to clear it or because you don’t have time, your ingot loot will drop precipitously (2.0~2.45 modifier is half as many ingots per drop as 3.5+).
The more times I explain it, the more I’m convinced that the delve loot system was designed to be intentionally obtuse to prevent people from finding out exactly what drops they got, and, by extension, the cost/benefit for actually (irreversibly) raising delve level.