Well, as usual, we are all mindreading. I didn't see anything about "owner" and I didn't see anything about "has only SE." What I did do, is the math, that the amount in question is half the allowable amount  for an employee, as if someone wants to use Employee + Employer Match, which isn't how SIMPLE IRA plans would work. That's why I put it in the form of a question.

Details matter. More details always help. Specific details make a difference.