It was said that Satoru was disabled. In what way exactly? here’s the link. ht...

I am assuming that disabled was supposed to mean transfer but got lost in translation or something. (the character could have been messed up even)

I mean disabled makes sense in this page but it really doesn't connect with anything else in the story at all.

There were some mishaps like that through out the manga (I.E. Satpru saying that even if he would have received the letter properly, he still considered Shiro as only a friend, when previously he said that he started avoiding Shiro in middle school because he had feelings for him), so I'm not sure if it's the translation or a mistake of the mangaka.

I think it was mistranslated. Here's another page:

http://www.mangago.me/read-manga/time_lag/an/time-lag-chapter-3.html/14/

I don't think it was actually his birthday; I think she meant he forgot to bring his lunch with him (which he did refer to later in the chapter).