Made a clerical error in my UK visa application. Should I be worried?

I had noticed an error in my visa application, and upon calling the phone services, was advised a hand written change would suffice (I had written in the wrong year for a travel trip).

I also wrote a letter explaining the error and the change.

Today at my biometrics appointment, when I mentioned the change, I was told too bad, nothing can be done and they didn't scan the page with the correction. They did, however, scan the letter I wrote with the explanation and saying it's an error. There's just no change for them to look at.

Will this adversely effect my application? The wrong year doesn't match the rest of the dates in the application, or my passport. My letter that states the right year makes it make more sense but will they ignore the letter as there's no physical correction on my form?

Obviously I'm stressed. I'd hope a small mistake isn't super punishing cos I'm sure I'm not the first to make a mistake!