Is this Hollow Heart (potatoes)?

[Susa]

Today I dug up a few potatoes and when I cut them open after cooking I saw a small, mushy hollow in the center. It was the same color as the rest of the potato. Is this Hollow Heart?
Also, the potatoes I planted are the small red ones and yellow ones...are these what are called 'new potatoes'? I'm just wondering because I only got 2-3 potatoes from 1 plant and I read somewhere that some varities potato plants will only produce this small amount.
Thanks

[DoubleDogFarm]

A "new" potato is a young uncured potato from any variety. You harvest new potatoes early, a few weeks after the potato plant flowers. They have a thin skin and are eaten fresh, for they will not store.

Eric

[Susa]

So if the potatoes are left in the ground for a longer period of time they can be stored once harvested? How long do they need to stay inground? We have a ton of June bug grubs in the potato bed, so would it make more sense to just harvest/eat them quickly or will the grubs not bother them?