they are just asking for your opinion on the text?? Is that possible at all, as in a review to know how well this person is translating.
If not, and they actually expect you to correct the text, I would not accept a fee of one hour for 4,000 words, since almost certainly, it will take you longer than that. If so, you should ask them to send you the text and then agree on a per word rate, or just quote them your hourly rate to revise the text to their standards.
Best of luck,
I never accept hour rates for proofreading, I always charge per word in the text to be proofread.
This way I don't risk spending 3-4 hours, when the client is only paying for 1 hour.
Of course, you should always have a look over the translation first to make sure if this is a good translation or not.
Poor translations may take forever to correct, and you will be responsible for delivering a decent job.
In other words: I would not accept this job "as is", but ask for more hours to complete it or for a rate per word.
Have a nice weekend.