TIFU by not double-checking calculations for a procedure

Hello Reddit, long time lurker, first time posting on this thread so here goes. Also, not a native English speaker, so please pardon any mistakes.

To give some background, I work in a university research laboratory (just undergrad work, nothing too fancy). My project includes synthesizing a metric borkton of chemicals and studying their behavior. The FU happened in the synthesizing step.

About last year when I started the project, my advisor gave me his standard method of performing the chemical synthesis. After a couple rounds of failures I'd figure something must be changed in the calculations that form the basis of the synthesis.

This took a while, but eventually blockhead me thinks he got the answer. Sent an email to the advisor and he gave me the go-ahead (also another TIFU - me thinking the advisor would do more than just glance at my work).

I went on with my project, powering through the arduous synthesis process. This took about a year, and the results on the premises was very promising. It was so exciting - I was on the cusp of having my name on a research publication! I did notice that a number (we'll call it number A) looked funny, but never really thought of it. At this point, I was starting the part where I study the behavior of my chemical.

Then comes last night. I had a couple weird results in the behavior study and came to my advisor to talk about it. He mentioned that number A is a pretty important factor, so I mentioned my weird feeling about it to him. Now, I've had my share of mistakes and have been called out on them, but his "you did WHAT" stare that time will probably etch itself forever in my brain.

We ran through my calculations again. It turns out that while fixing my calculations, I managed to bump number A out of its acceptable range. While it did solve the problem I mentioned initially, it created other problems - I was making the desired chemical, but its quality is low enough to create problems later on.

Since I was using this whole procedure for my work throughout the year, it means that all of my work through the last year might be in vain - I may have to restart everything.

Right now, I'm working with the advisor to see what we could salvage. He told me that things like these do happen in research, but I feel very bad. I feel as if I've let him down, and wasted his resources on something that could have been avoided had I been more careful. It's not all bad - since I'm familiar with the procedures now, I could make up for the losses in less time it took for me to do it in the first place. Oh well, it is what it is.

TL;DR: Did not double-check a calculations made for a research procedure, ended up doing it wrong for a whole year before realizing, wasting a year's worth of time and resources.