Awakened Added Lightning Level 10 states +2 Lightning Gems but only gives +1

The Awakened Added Lightning Damage Support states that it is giving +2 to Level of Lightning Skill Gems when it reaches level 10, however it is only giving +1.

Level 10 is reached by: Level 6 support, +3 from Venarius Astrolabe, and +1 from Runegraft of Gemcraft.

However, with another +3 to Skill Gems from Venarius Astrolabe, Spark of the Nova only reaches Level 25 (21 from gem, +3 from amulet, +1 from support is listed)