For reference Ambrosium is essentially The Aether's equivalent of coal, tools are repaired in an altar which is made from holystone surrounding a Zanite gem (probably equivalent to cobble surrounding gold or iron), Shards last 12.5 seconds or 250 ticks of "repairTime". (It works like a furnace.)

Ambrosium Shards consumed | Time in seconds to complete repair | "repairTime" defined in the json file (repair time is in ticks)
1______________________________| 12.5_________________________________| 250
2______________________________| 12.55________________________________| 251
2______________________________| 25___________________________________| 500
3______________________________| 37.5_________________________________| 750
I don't think equipment damage effects the process, a sunhat with 1 damage still consumes a full ambrosium & takes the full 12.5 seconds when set to a "repairTime" of 250.

Adjust the "repairTime" values as you see fit. I have not balanced these values with rigorous playtesting I could send a rebalanced version later if you want me to:

The json files go in data>dwmg>recipes>aether

1.19.2:
necromancer_hat_repairing_1_19_2.json
netherite_fork_repairing_1_19_2.json
peach_wood_sword_repairing_1_19_2.json
reinforced_fishing_rod_repairing_1_19_2.json
sunhat_repairing_1_19_2.json

"category": "enchanting_repair", is only for 1.19.2, any version apart from 1.19.2 doesn't need to state the category. If 1.19.2 is missing the category, then multiplayer will fail to work when the Aether is installed.

1.20.1/1.18.2
reinforced_fishing_rod_repairing.json
sunhat_repairing.json
necromancer_hat_repairing.json
netherite_fork_repairing.json
peach_wood_sword_repairing.json

The aether github examples:
1.19.2:
https://github.com/The-Aether-Team/The-Aether/blob/1.19.2-develop/src/generated/resources/data/aether/recipes/bow_repairing.json#L3
Everything else:
https://github.com/The-Aether-Team/The-Aether/blob/0a3dbfe34318b7568ed88bfb8d63bfd951023e06/src/generated/resources/data/aether/recipes/bow_repairing.json
Groups on 1.19.2:
The-Aether-Team/The-Aether@38c8685