#also interestingly the name for his mom on the player profile is completely different from the name on the bank card according to someone

[breadandlottery]

The first PIN Gi-hun enters for his mom's bank card is 0426. When it declines he says "It should be my birthday" implying that his birthday is what he already tried... but later in the season we see October 31 is his birthday.

Someone on Reddit pointed out that June 8 2010 would be 04/26- 26th day of the fourth month- in the lunar calendar... however according to Gi-hun's player profile, his daughter was born in 2011, not 2010. The player profile also lists her birthday as June 9, though, so it is potentially inaccurate. (It does confirm his birthday as October 31.)

But then also:

He's typing in the PIN at like exactly 4 minutes and 26 seconds into the episode.

I don't really think this is important to the story but I do find it neat and I think 0426 or 4/26 must have some special significance to Hwang Dong-hyuk, like a friend's birthday or an anniversary or something. Which, if true, is super cute of him to work it into the show.