Firstly - you have a typo in your second sentence - you missed out the 'that' after 'at'.
And - as Adrian pointed out, your sentences are a little awkward. You would be better to use 'some' rather than 'that'.
But, to your question: Assuming you are using 'some point' as an example, e.g. 'It will be done at 5 o'clock today', vs. 'It will have been done at 5 o'clock today', the difference is the time that the thing will be done. The 'will have been done' form is like a progressive tense. It means that the thing will happen some time between now and the specified point in time. It doesn't say when, it only says that it will have happened by that time. The 'will be done at' form specifies the exact time it will happen.
It's also a lot more natural with the 'have been done' form to use 'by' rather than 'at'.
You need your ticket printed? It will be done at 5 pm. -> At 5 pm exactly, someone will print it.
You need your ticket printed? It will have been done by 5 pm. -> Someone will print it, sometime before 5 pm. If you come at 5 pm, it will be ready for you to pick up.
Hopefully I haven't made too many typos myself, and hopefully it's clear?