What is the duration of the Challenge (exeta res) spell?

Question

When I cast exeta res on a monster that runs with low life (like Hydra), it avoids the monster from running. But after some time the spell stop working and the monster runs away again. How long will the spell keep the monster from running?

Answer 1

exeta res makes all creatures nearby change their target to the caster for at least 6 seconds.

Comments

Where did that number come from? Is this an official number or did you do some experiments to find this number?