How long will this script actually run?
Paste the narration. The rates are measured off produced episodes at speaking pace, which is why they are slower than any reading-speed figure.
Why a Korean script fails an English gate
English runs at roughly 2.6 words per second; Korean at roughly 6.4 characters per second. They are not the same unit. Point a character-count rule at an English script and it over-estimates the runtime by about double, so perfectly good scripts get rejected wholesale. This is the exact wall a Korean channel operator hits on the day they open an English one.
Bound it on both sides
A length rule with only an upper bound produces thin episodes that pass. The band matters more than the ceiling: too short and the hook has nowhere to land, too long and the retention curve breaks before the payoff. Derive the number, do not assert it — and be able to say what breaks one second either side of it.
Speaking rate is not reading rate
These rates are measured off synthesised narration at production pace, with sentence pauses included. A rate taken from a reading-speed study will be faster and will under-run.