Am I right in reading that the file you are trying to upload is only ~16MB? What's generating/where are you seeing that message?
OctoPrint's default maximum upload size is 1GB, which is configurable in config.yaml (link to docs). Since you've said you installed it through a home assistant add-on, I wonder if this is what is restricting the file size not OctoPrint.
I don't know where config.yaml is but I would expect that whoever made the add-on you are using might have documented it somewhere.
If the default is 1GB and your file is 20KB, then I don't think OctoPrint is the problem here. I am wondering if there is something in the add-on that is causing an issue. I have no idea how it works to guide on that.