I think the calculator thing shows Philip's background and generation. If you were circa 40 yo in 1987, you grew up with slide rules and *maybe* mechanical adding machines. So Philip might not be used to using spreadsheets to track all of his invoices right down to a line by line day to day thing, but would probably be doing his P&L on a weekly or monthly basis.

(today I think it'd be almost routine, since you could separate out the accounts payable and receivable by date, etc)