The cost behind
the headline.
Use one currency and one deduplicated incident cohort. This is an economic worksheet, not an accounting statement or scheme ratio.
Count the loss once.
Do not add both reversed sales revenue and merchandise cost as separate losses. A fraud report, refund and chargeback may describe the same incident. Recoveries must offset the same cost basis only once. Estimated missed legitimate contribution margin is shown separately from realised loss.
Use mature outcomes and record the cohort and observation date in your own working notes. Negative net direct cost indicates recoveries exceed the entered cost basis; investigate the inputs before interpreting it.