I looked around but didn't see an answer. It is stated about spawnpoints

Spawnpoints cast spells the same way your Mage does, using the target and range shown on the spell. Always count range from the Spawnpoint (instead of your Mage). The Spawnpoint must spend its own mana first (by removing mana counters). If the Spawnpoint does not have enough mana to cast the spell, you must pay the difference from your Mage’s Mana Supply. You control all spells cast by your Spawnpoints.

It must spend its own mana first, however does it have to spend ALL its mana first. Had someone have a temple (which you must have at least 2 mana on it before you can cast a creature). He had 6 mana on it, but only used 4 from the spawnpoint and the rest from the mage, so that if he wanted next turn he could cast something else, because it only gained 1 mana per turn. Because the rule doesn't say ALL we let it go. Which is right?

Cheers