All of this. 6 is good if not great. But yeah you're going to find readers that just aren't the right fit. I had one lady who did the job, but it was clear from her notes that she really wanted my Sci-fi book to be a romance, and her feedback was written accordingly to try and adjust it into that. Another guy wanted to turn my work into more of an action tale, cutting world building/thematic stuff in favor of hammering it down into a much more commercial formula, missing the point of certain characters and events entirely. He even started to get facts about the story wrong, as if he wasn't actually reading it closely anymore. Then I had one beta reader who really got what I was going for, and pointed out lots of great things to make adjustments on, clarify, and generally guide the story away from some of its bigger issues. The others periodically had useful things to say, but yeah you're going to find you'll have to wade through the group to find the feedback you feel is actually pertinent.If you've never had any beta readers before, I'd say it's a good idea to get as many as you can, with the goal being to "shortlist" readers who's input you find valuable. Keep in mind that not all beta readers are going to be a good fit for you and the kind of writing you're trying to do, even if they're in the same genre. If it ends up you find ALL of these potential readers give you good input that you feel improves your work, then by all means, keep 'em around, having too many beta readers is a good problem to have. But most people will find that good beta readers are in short supply as some people just never get around to reading your book, some are more interested in insulting or cutting down perceived competitors/threats than providing genuine editorial insight, and others just aren't good beta readers, even though they mean well, and aren't giving you the kind of actionable insight that is useful to you.