Eldritch Smite: is the damage intended to be 1d8 for using the Invocation itself in addition to the 1d8 per level of spell slot used?

concerning Eldritch Smite: is the damage intended to be 1d8 for using the Invocation itself in addition to the 1d8 per level of spell slot used? So a minimum of 2d8 damage? believe just 1d8 per level, so minimum 1d8

— Mike Mearls (@mikemearls) March 14, 2018