3500 calories/1lb lost

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I'm curious how exactly does this work??? So every day I should burn 3500 calories? I think that's nearly impossible. Should I just burn 3500 weekly, have 3500 difference from my recommended intake to maintain, or am I really supposed to burn 3500 daily. My ultimate goal is to become lean. Not big on what the scale says anymore just looking reduce body fat while gaining lean muscle.