This is a PerfCounter64 counting upstream Forward Error Correction (FEC) errors on an xDSL line, recorded in a historical performance bin. It tells an administrator how many upstream bit errors the DSL line's FEC mechanism had to correct during that interval, an early indicator of copper-line noise or attenuation problems. For example, an upstream FEC count that climbs steadily across successive history bins on a customer's DSL port would point a technician toward checking the loop wiring before the errors escalate into dropped sync.