Am I getting the Entrance spell correct?

--As a 1 round spell it can be used on any creature of up to 5 levels or HD.

--But for each extra round spent staring at the opponent the level maximum increases by 2, until 16 be reached, after which no further staring will help.

So if Jack the Stygian stares at Joe the Barbarian for 3 rounds and then casts, Joe is susceptible to the spell, as long as he is no greater than 11th level --5+ (3x2)--(Will save applies). If Frank the Barbarian is there and is 17th level, he is completely immune to Entrance.