It's the same for External Detectable IDs and External Sealable IDs. An example from my log:
Code:
[01:29:01] [Client thread/INFO] [Galacticraft/GalacticraftCore]: [config] External Detectable IDs: the use of numeric IDs is discouraged, please use minecraft:coal_ore instead of 16
[01:29:01] [Client thread/INFO] [Galacticraft/GalacticraftCore]: [config] External Detectable IDs: the use of numeric IDs is discouraged, please use minecraft:diamond_ore instead of 56
[01:29:01] [Client thread/INFO] [Galacticraft/GalacticraftCore]: [config] External Detectable IDs: the use of numeric IDs is discouraged, please use minecraft:gold_ore instead of 14
[01:29:01] [Client thread/INFO] [Galacticraft/GalacticraftCore]: [config] External Detectable IDs: the use of numeric IDs is discouraged, please use minecraft:iron_ore instead of 15
[01:29:01] [Client thread/INFO] [Galacticraft/GalacticraftCore]: [config] External Detectable IDs: the use of numeric IDs is discouraged, please use minecraft:lapis_ore instead of 21
[01:29:01] [Client thread/INFO] [Galacticraft/GalacticraftCore]: [config] External Detectable IDs: the use of numeric IDs is discouraged, please use minecraft:redstone_ore instead of 73
[01:29:01] [Client thread/INFO] [Galacticraft/GalacticraftCore]: [config] External Detectable IDs: the use of numeric IDs is discouraged, please use minecraft:lit_redstone_ore instead of 74
The External Sealable IDs info will be in the log only if there was an Oxygen Sealer used in the world. Look in the log after the player joins the world.
You can use metadata as well, for example modname:block_name:5 where 5 is the metadata. If you don't specify any metadata, Galacticraft assumes metadata 0 for External Detectable IDs (so only metadata 0 will be detectable), and all metadata for External Sealable IDs (so all different versions of the block will be sealable).