Why do i need to enter business expenses in personal after already entering them in business?

[JulieCo]

Don't enter your business expenses again if you have already entered them in the business section of TurboTax. 

You might be at the job-related expense entry section of TurobTax which is only for expenses that are unreimbursed from a W-2 employer.  For 2018,  job-related expenses are not deductible on a federal return, but some states still allow the deduction so that is why there is a section for them in TurboTax.