From what I can tell, prior to mid-2017 (which would include most or all of the period that the lawsuit covers) SolarCity's residential products were actually 20-30 year leases rather than outright purchases. Following GAAP accounting rules, the revenue from the lease payments would need to be spread out along the whole length of the contract, so a lot of the fake revenue that they are talking about might actually be anticipated future revenue spread across the next 20-30 years rather than revenue when the sale was made. 50-500 million spread across 25 years would be 2.5-25 million per year, which seems much more reasonable as a proportion of revenue that could potentially be faked.