What is the difference between the add rune symbol and the generic rune (circled number) symbol?

Ruling: Numbers are energy symbols, while other symbols are power. An ability showing a circled number and a rune symbol means you exhaust a rune and recycle a rune of the specified color (these can be the same rune).

Nuances:

• The exhausted rune and the recycled rune can be the same rune
• Some cards provide power directly by exhausting them, which can substitute for recycling a rune to generate power