Your goal, your rules. I personally don't count a book read unless I read it all, but I don't think it's cheating if you count a book that you read the parts you wanted to read.

I set a variety of reading goals each year and I like to be clear on my own rules for myself, but I also reserve the right to change the rules later if what I set up stops working for me.

When I participate in a reading challenge and my reading log, I only count books that I've read from start to finish. However some goals that I set for myself I will count partially read books. For example, this year I have a goal to read or DNF the last 20 books that are on my physical shelf and that moved with me 3 years ago. If I start the book and decide I don't want to finish it, it goes into my pile of books to get rid off and I check it off my list.

I recommend you decide what your goal is for that book and then log it in whatever manner feels right to you.

I'll say I do like that I can mark a book as DNF on Storygraph. You can also create a shelf on GoodReads for partial reads or DNF books, but only if you feel the need to keep a record of it.