The two different magical rings shared two out of three sets of runes. The first set would enhance Lith's energy signature so that the mana flow originating from the crystals embedded into the rings would offer less resistance to the Forgemastering process.
The second set amplified the effects of the rings' pseudo core, allowing it to be temporarily boosted when necessary.
The third set of the magic holding ring allowed for energy manipulation so that the spell could be used a little at a time instead of being released in one go. Also, as long as the stored spell wasn't completely spent, the runes made it possible to recharge or amplify it on the fly.
In the case of the barrier ring, instead, the third set contained a complex pre-set code that would allow the ring to channel Lith's mana into a spirit magic barrier even if he had no idea how to do it himself.
