If multiple sources would deal damage to you at once (for example, several attacking creatures), 1 damage from each of those sources is prevented.

Damage that would be dealt to creatures you control is unaffected.

If a prevention effect applies to noncombat damage that would be dealt to you while you control a planeswalker, you choose whether to apply that prevention effect before or after the planeswalker redirection effect. If you apply Protection of the Hekma's prevention effect first, the planeswalker redirection effect still applies to the remaining damage. If you apply the planeswalker redirection effect and your opponent chooses to have the damage dealt to a planeswalker you control, none of that damage is prevented.