Would a card like boros reckoner have 6 devotion to red and white or 3 because the devotion description sais mana symbols and there are 3 red and white mana symbols in boros reckoners mana cost
Hybrid mana count as 1 for each of their colors, but only 1 towards hybrid Devotion. Boros Reckoner provides 3 Devotion to red, 3 Devotion to white and 3 Devotion to Red and White. Devotion is more 'How many symbols have one or both of these colors?' Than 'How many of these symbols appear.'
3. It checks each mana cost and says "Hey, I'm looking for white or red. They're both there! That's 1.." And goes to the next. Think about it like this, a card cannot, ever give more devotion than it's converted mana cost. So Reckoner has a 3cmc, and therefore cannot grant more than 3 devotion in anything, regardless if it's white, red, or both :)