About time??
Numerator finished and asked the professor to return before he regretted everything, and sent them all to a bottomless pit, a repeating decimal.
A student seated behind Caius sighed in relief because they had missed that subject, and muttered, “About time! We’ve managed to survive this class, but I dread to think what they’re gonna do with us now.”
After the last lesson, Denominator thought the lessons had been enough to discipline the students and proceeded to explain their next task.

I would like to know what does "About time" here mean. Thanks.

Question

About time??
Numerator finished and asked the professor to return before he regretted everything, and sent them all to a bottomless pit, a repeating decimal.
A student seated behind Caius sighed in relief because they had missed that subject, and muttered, “About time! We’ve managed to survive this class, but I dread to think what they’re gonna do with us now.”
After the last lesson, Denominator thought the lessons had been enough to discipline the students and proceeded to explain their next task.

I would like to know what does "About time" here mean. Thanks.

Answer

'About time' means 'finally' or 'at last'. It is said when you have been waiting for something for too long. The waiter finally brings your food, so you say 'about time'. Although best to say it to yourself and not the waiter, as it would be considered very rude!