It's not your fault. There's no space in the document. It's a genuine error on my part that I've gotta fix quicklike. And the other archetypes specify that you gain "a 1d6 psi dice" for clarity. I just missed the Mind's Eye on my second pass.
Though if you grab one of the Psionic Heritage Traits (like Wild Talent for humans) you can gain additional Psi Dice that way, as well as access to a power you can spend your Mind's Eye psi-dice to manifest because psi-dice are entirely interchangeable.
Whether you're an Adept, an Esper, or just Psionically Gifted.
But. Only psionically gifted characters and Espers ever increase the -size- of their Psi Dice. So it's possible to wind up with differently sized psi dice in your reservoir. Say you're a multiclass Esper/Adept with Mind's Eye, as example. 10 and 10. You'd have 3d6 from Adept, 5d10 from Esper, and if you were a Wild Talent, without the Wild Paragon trait, you'd gain 1d4.
You could use your D10s to improve your Combat Maneuvers, the d6s to use your Wild Talent Telekinesis or Telepathy, and the d4 to augment an Esper Power. They all improve things to a similar degree. It's just a question of how quickly you lose a given die.