Please help :(

Someone help me...what number do I put on my w-4?? I’m uneducated on this topic and didn’t know what to put so when I first got hired my manager filled it out for me....I’m now realizing I’m getting too much taken out . Everyone gets $80 or less and I get $200 taken out, it’s bull 😞. How does this all work?? I’m 18 now was 17 when I got hired, she didn’t even offer for me to take it home/talk to my parents about it .