From Beckett's, "2001 Quantum Leaf was initially released as a 260-card base set...Later in the season, card numbers 261-290 were issued as part of a wrapper redemption (24-wrappers plus $6.99)." Beckett list cards to 296 (there's no #293) with no explanation about the 5 extra cards. I found one site selling the 35-card Update set. So maybe Beckett just has a typo.
If the only way to obtain the Update was by mail-in redemption, then they wouldn't be listed as part of the base set. But that makes no sense since I've seen the Red, Green, and Purple Infinity parallels for these cards. So the Update cards must have been distributed other than just mail-in redemption.
IMO the bottom line is this; Base set checklist needs to match the Infinity parallels; numbered to 296 (no 293).
Someday my cards may double in value and then be worth half of what I paid for them.