Newbie Mistake? Or Just Bad Karma?

So I started my new job as an accountant a month ago. You know how you feel like everyone's watching your every move the first few weeks, and it takes ages to get comfortable even asking for help with anything that’s not completely basic? Yeah, me too. Fast forward to today: we're doing quarterly reports at our weekly meeting, and my manager calls out a number that doesn't match what I've been reporting all week. He's a bit of an ass, no offense, but he just says the words and moves on. The whole table looks like they feel for me but don’t know how to ask if I’m okay. I admit, I went straight home and cried over it for two hours. But the next day, when I had cooled down enough to look closer at where I'd messed up, I realized my mistake was because someone else hadn't entered a transaction from last month properly in the first place. So it’s not like I didn’t check or anything, it's just that their previous error made me miss this one. Thing is, when I brought it to my boss and offered to fix things myself with an explanation attached, he still seemed pretty unimpressed. And while everyone else seems totally chill about me having a bad day, there’s this weird vibe from some of the older guys in the office that they’re disappointed or something. Am I just reading too much into it? Or should I try to explain more and make sure people know I'm not an incompetent idiot who can't even do basic math? It feels like such a small thing, but at my first job ever, you’d think everyone would cut me some slack if they were me. Maybe I’m the asshole here for thinking it’s okay to make mistakes when you're new, or maybe the office is too stuffy and unkind about them. I really don't know.