Job description poorly described. Should I take that job?

[eric5037]

Hi, 

I have agreed with a client to perform a task A. Initially, there were 2 tasks: A and B but he doesn't need the task B anymore. 

He has just sent me an offer but the job description is still with task A and B. 

I have asked him to edit the job description but he tells me it's not possible. There is a pdf specification file where it appears clearly that task B is not needed anymore but can I rely on this.?

What should I do?

Shoud I accept the job relying on the .pdf specification file that is explicit enough about the fact that the client needs only the task A and not the task B even if it's not the same as the job description?

Is he mistaken when he tells me that he can't edit the job description?

When can a job description be updated? before hiring? after hiring?

Thank you.

UPDATE: the client has just changed the job post but not the offer. 

[eric5037]

I answer myself if that can help someone with the same issue or doubt: 

it's perfectly possible to change the job post and the offer. no need to cancel the offer and create a new one. my client has just done it and told me it was a bit ambiguous and that's why he wasn't able to it in the first place.