If you are getting pieces of cues you already own in your Surprise Boxes, worry not!
There is a randomized side to Surprise Boxes that works a lot like trading cards. Initially, the first packs of trading cards you purchase will always be filled with new cards you still don't own. However, the more cards you have, the more likely it is for you to get repeated cards along the way!
It will be exactly the same with Surprise Boxes and that is why, further down the line, you will get some repeated cue pieces. Whenever this happens, though, they will count towards upgrading your collection cues.