It does sound like an error. Imagine seeing your heart on the echo and each time it pumps, it goes almost completely flat, squeezing out every milliliter of blood. That's what 98% would amount to. Even 92% would be a pretty flat heart. Definitely ask the cardio about this one.
It is possible to have a high EF, but it could also be a heart that is compensating for a deficit in the circulation system. The normal range for EF (ejection fraction, amount of blood pumped with each heartbeat) is 50 to70%. When the EF is in the upper range, there is more blood pumped with each heart beat to maintain a balance of blood flow in equilibrium between the right and left side.
Or for some pathological reason, the heart is pumping harder than normal. You should get an explanation from your cardiologist. It may be just a blip and insignificant.