Methodology
Each day is the out time minus the in time, minus the unpaid break. If the out time is earlier than the in time, the shift is counted as running past midnight and 24 hours are added. Days are added together in minutes, and the decimal figure is worked out once from the total minutes (minutes ÷ 60, two decimal places), so the decimal always matches the hours:minutes figure.
Rounding, when you turn it on, applies to each in and out punch, never to the break: to the nearest 5 minutes, 6 minutes (a tenth of an hour) or 15 minutes, where 1 to 7 minutes past the quarter hour round down and 8 to 14 round up. This follows the federal rule in 29 CFR 785.48.
Overtime follows the rule you pick. Daily overtime counts the hours over the daily limit on each day first; weekly overtime then counts the remaining regular hours over the weekly limit, so no hour is counted twice. The federal Fair Labor Standards Act sets the weekly limit at 40 hours and the overtime rate at not less than 1.5 times the regular rate (U.S. Department of Labor, Fact Sheet #23). Some states, such as California, also count daily overtime, so both limits can be edited. For cards of 8 to 14 days, every 7-day block is measured against the weekly limit by itself.
Gross pay is regular hours times the hourly rate plus overtime hours times the rate times the overtime multiplier, rounded to the cent once at the end. It is pay before taxes and deductions.
Every release is checked against a fixed set of worked examples, including overnight shifts, long breaks, rounding edge cases and daily plus weekly overtime, before it is published.