If the Feywild Shard magic item’s Wild Magic Surge results in a spell, does that replace the initial triggering spell, or occur in addition to it?

Tasha’s Cauldron of Everything (p. 127) includes a magic item called the Feywild shard. The relevant part of its description states:

When you use a Metamagic option on a spell while you are holding or wearing the shard, you can roll on the Wild Magic Surge table in the Player’s Handbook. If the result is a spell, it is too wild to be affected by your Metamagic, and if it normally requires concentration, it doesn’t require concentration in this case; the spell lasts for its full duration.

This part is the one that some in my group don’t agree on:

  • My reading: You cast a spell that is being affected by Metamagic. You then choose to roll on the table. If the resulting effect listed on the table is then also a spell, it is separate from the original spell and has the two listed added conditions (Metamagic can’t be used on it, and it doesn’t require concentration).
  • The others think that if the result of the roll on the Wild Magic Surge table is a spell, it replaces the original spell, and the original Metamagic option you chose doesn’t affect it.

Which interpretation is correct?