It seems like the going rate for drawing two cards is two mana with a drawback these days. I tried to make a visual throwback to Council of the Soratami.
Are those plus-symbols supposed to be mana symbols?
Riotous Growth - Sorcery - Draw a card, then you may put a land card from your hand onto the battlefield. Then Riotous Growth deals damage equal to the number of lands you control to target creature.
I think it's a special mana symbol they created to indicate that this mana lasts until the end of turn and does not empty in between phases like normal mana. I'm willing to bet though that the vast majority of Magic players would not understand the nuance, because 90% of the time it does not affect gameplay whatsoever. So it is no surprise you got confused. Took me a few minutes to understand it too.