Hola Goo

Sorry to have confused you with those three specific verbs on that list. 

They were meant to show the infinitive only "comenzar, empezar, negar".

They word they were showing in front is their conjugation (yo form) of their preterite tense. This was showing because, by mistake, the system took those forms from another list.

Now that you asked, those are from another list that shows verbs that undergo a consonant/vowel change when conjugating them in the preterite, so:

negar - yo negué 

comenzar - yo comencé

empezar - yo empecé

I hope this clarified it.

Saludos

Inma