'It's time to upgrade the thief's space again!'
Ace has been planning for this upgrade for a while now and collecting all the grade-5 storage rings needed.
But a grade-5 storage ring wasn't made in the outer provinces, and he only came in contact with them when he robbed Archie of his identity.
However, even then, he only got just 3. Even after requesting specifically for these rings from Harvey, he only got 56 because they were all in stock then.
Harvey could even take that many outs was all because of his status, or no matter what, this many grade-5 storage rings were almost impossible to acquire unless you're a student of a Royal Demon Institute, of course.
So, Ace wasn't too worried about not getting the remaining rings in here, and as he thought, the institute had them. This also proves the fact that their treasury won't be easily theft.