Earth Sphere Smash Attack X?

The Fey Earth Sphere T2 trait 'Smashing Blow' grants Smash Attack. In the abilities section, Smash Attack is listed as 'Smash Attack X', granting the possibility to hit other opponent models within X inch. It does not mention a default value for X when it is not stated with the granted ability (as is the case with the Fey Domain).

Question here being: what is the default value for X for the ability Smash Attack, and does the Fey Domain Earth Sphere trait deviate from this?