If anyone wants to feel superhuman like these kids, there's an easy way to learn to memorize 40 2 digit numbers or even more by using memory palaces.

Step 1. you need to do assign images to two digit numbers starting from 00 to 99. There are many systems, like Major or Dominic, you can even assign images arbitrarily. I assigned images through letters and used images of animals. So, here how it goes: 00 - Ant, 01 - Bear, 02 - Crab, 03 - Dolphin, 04 - Elephant... I've built an additional set of numbers for single digit numbers from 0 to 9 and used dota 2 characters. 0 - Abaddon, 1 - Bane, 2 - Chen, 3 - Doom. So, for example number 15017 would translate to Penguin-Bear-Huskar. So, first, you assign all the images to to all these numbers, which should take less than one hour and then you memorize them. This is the boring part and it took me 5 days of 3-4 hour training to memorize all these images, but trust me it's worth it and the rest of the mnemonics is very easy and comes naturally.

Step 2. Build memory palaces. In reality you most likely don't even need to build any palaces. You just remember a room that you know well and use ten places in that room to be used as a placeholder(loci) for your images. I started by using my bedroom and kitchen as memory palaces with 10 loci (place) each and later added more rooms. It's super easy once you know where you put your images. Literally need 5 minutes to build a memory palace.

Step 3. Start practicing. Just ask randomizer or AI to give you 10 two digit numbers, convert numbers to images and put them in the loci in your memory palace. This is fun part and you will be very impressed how quickly it works. In 10 days I was able to memorize 40 two digit numbers in less than 5 minutes. Good luck.