Each voice-over can read up to 5,000 characters, about 5 to 6 minutes of speech, and you can make up to 10,000 characters of voice-overs a day.
You may also see:
"Voice-overs can be up to 5,000 characters. Shorten the piece to add one."
"That is more than today's voice limit ([number] characters left)."
"That would pass today's voice limit of 10,000 characters. It resets at midnight UTC."
"This piece is [number] characters. Voice-overs can be up to 5,000; select a shorter part."
What to do
In the editor, the voice-over in the Media tab reads the whole piece. Shorten the piece, or copy the part you want into a new piece.
In Videos, open the Audio tab, tap Generate voice-over and edit the Script box to the part you need.
Put directions in square brackets on their own line, such as [B-roll of the office]. They are not read or counted.
For the daily limit, continue after midnight UTC (1:00 am in Nigeria).