Cannot reproduce your output with the latest version online:

clingo version 5.7.2 (6bd7584d)
Reading from stdin
Solving...
Answer: 1
choose(-1)
Optimization: -1
OPTIMUM FOUND

Models       : 1
  Optimum    : yes
Optimization : -1
Calls        : 1
Time         : 0.021s (Solving: 0.00s 1st Model: 0.00s Unsat: 0.00s)
CPU Time     : 0.000s