Will post soonish, but I believe if you spend a Ki point you get [i]two[/i] sun bolts as a bonus action, similar if you were doing a flurry of blows.

 I’ll admit the wording sorta makes it confusing, however I believe that since monks will later get an extra attack and thus they could potentially already use Sun Bolt “twice” without a BA once they get to level five, the twice in the sun bolt’s Ki BA likely refers to being able to use two attacks as a BA.