Automate formulas depending on number of records

Hello,

I have a spreadsheet I am using to track people as I collect an item from each of them. Each of these items has a barcode. I am using a handheld scanner to scan the barcode into my "Scan Sheet" which will then update a few fields, including "Scanned", "Not Scanned" and a separate sheet for "Missing People". In a few areas of my spreadsheet I need to manually update certain cells or columns depending on the amount of records on the data sheet. I know this could be done better or differently.

This sample sheet has 6 records. If there are extra records entered onto the Data sheet, I need to manually update column D by dragging the formula down to match the amount of users. I'm sure there should be a better way.

My Scan Sheet is where I do the scanning to enter the barcodes, it has a running total for number "scanned", right now the formula needs to be updated manually depending on the number of guests. I'm sure there's a simple, better formula.

Last my 'Missing People' sheet has a list of all people, unless they have been scanned then the row is blank. There might be a better way to collect this data, but what I have works, I would just prefer if the blank rows were removed automatically for easier viewing.

Hope this all makes sense, appreciate any help improving this spreadsheet!

Thanks,
Chris