Not until the last moment did he figured out the answer.
Not until all the people had left did he got out of the classroom.
You can find out from the cases above that when 才 means ”not unitil" it's often used with the word '到". And as you many know "到" means "until" in Chinese.
You can omit the word 到 in some cases. for example:
In addition, 才 often means the action is conducted late.