Eufy E28 Floor Cleaner - Not being used?

I just bought another floor cleaner as I have had my machine since probably October or November of last year. I run it several times a week if not every single day. I was sure that the solution must’ve been emptied by now, but to my surprise, it was nowhere near empty.

Does anyone have any suggestions on this? Does the machine just not use a lot of cleaner? Can I put it in the clean water tank? Would love some suggestions and advice thanks.