Rule 820.1.d.1
When the additional cost is paid, the effect of the spell or ability, upon resolution, will be performed an additional time. Example: Desert’s Call is a spell with [Repeat] [2] and “Play a 2 [M] Sand Soldier unit token.” If its controller pays its Repeat cost as they play it, the card’s instruction to play a Sand Soldier is executed twice, as though the card says “Play a 2 [M] Sand Soldier unit token. Play a 2 [M] Sand Soldier unit token.” Example: A unit reads in part “When I attack or defend, you may deal damage equal to my Might to an enemy unit here,” and “My abilities have [Repeat] — Discard 1.” When its ability triggers, if its controller pays the Repeat cost as they play it, the ability’s instruction to deal damage equal to the unit’s Might is executed twice, as though the ability says “Deal damage equal to my Might to an enemy unit here. Deal damage equal to my Might to an enemy unit here.”