How did puck mess up by putting the potion in Lysanders eyes and screws up?

He puts the potion in the wrong set of eyes (Lysander's) and upon wakening the first person he sees is Helena. It's instant obsessive love........... for the wrong woman. Puck has messed up!

Puck spreads the magic potion over Lysander’s eyes, thinking Lysander is Demetrius. Lysander falls into love with Helena, who thinks he is toying with her. Then, Puck spreads the potion over Demetrius’ eyes, so that he, too, is in love with Helena. Helena thinks that both boys are cruelly mocking her, while Hermia is left alone and equally confused. Puck realizes his mistake, and makes amends by putting the potion on Lysander’s eyes once again, so that he may fall back in love with Hermia. This whole mix-up truly shows that you can’t choose who you love.