ECM Hours Exceptionally Low

[Yaya81]

Aside from a newly replaced ECM, is there any other plausible reason the mechanic's hour meter read 28 hours when hooked up to the ECM when the sellers indicated the boat has 320 hours? The mechanic indicated it didn't seem the ECM had been replaced as it has the original dates on it.

This is for a ZR6 409 in a Nautique SAN 230.