Is there room for installer error when cutting the airflow slot for The Edge Vent?

Yes, there is some latitude with the precise slot dimensions to be cut.

As with most building construction practices, there is some latitude with the precise slot dimensions to be cut for The Edge Vent's airflow slot. It is recommended that the lower cut for the slot be maintained as close as possible to 5" from the drip edge flashing and that the slot width be maintained between 3/4" to 1" wide (Note: An edge flashing must be used when installing The Edge Vent). A nice, straight lower cut will assist in properly locating The Edge Vent on the roof with the locating tabs on the underside the product.