It's not linear at all. We had our identity stolen through an insurance scam (somebody used our bank account and somebody else's name to open a policy with Progressive, which apparently does not validate ACH debits). This resulted in premiums of ~$300, $300, ~$500, $1002.96, ~$900, ~$900, and ~$3000 as the attacker presumably racked up huge fraudulent claims on the insurance company. The first 3 bills were reversed by Wells Fargo because their fraud policy covers fraudulent charges under $1000. The 5th and 6th were reimbursed because they were reported within 60 days of being made (and were under the limit anyway). The 7th didn't go through because we had detected the fraud and closed the account by then. But the 4th was just over the $1000 limit that they would reimburse, and so they were like "Sorry, nope, you're on your own for that one." We even filed a police report and waved that at them, and they said "We don't care. Company policy." So the very counterintuitive and non-linear result was that they paid for the $300, $500, $900, $900, and $3000 charges, and stuck us with the $1000 one, just because it was $2.96 over their limit. (Part of me really regrets declining to prosecute, but I had a ton of other stuff going on at the time and the last thing I wanted to do was get involved in a court case.)