Afterall - Additional premise or Counter premise

[shanmugavel]

According to Power score critical reasoning bible, After all was stated as Counter premise..
But in the following example given in the book shows that After all as an Additional premise. Below is that example.
" During last night's robbery, the thief was unable to open the safe. Thus, last night's robbery was unsuccessful despite the fact that thief stole several documents.After all, nothing in those documents was as valuable as the money in the safe."

The explanation given in the book is below:
Premise: During last night's robbery, the thief was unable to open the safe
Counter premise: despite the fact that thief stole several documents
Additional premise: After all, nothing in those documents was as valuable as the money in the safe.
Conclusion: last night's robbery was unsuccessful

Experts please reply...

Thanks in Advance,
Shan

[Geva@EconomistGMAT]

According to Power score critical reasoning bible, After all was stated as Counter premise..
But in the following example given in the book shows that After all as an Additional premise. Below is that example.
" During last night's robbery, the thief was unable to open the safe. Thus, last night's robbery was unsuccessful despite the fact that thief stole several documents.After all, nothing in those documents was as valuable as the money in the safe."

The explanation given in the book is below:
Premise: During last night's robbery, the thief was unable to open the safe
Counter premise: despite the fact that thief stole several documents
Additional premise: After all, nothing in those documents was as valuable as the money in the safe.
Conclusion: last night's robbery was unsuccessful

Experts please reply...

Thanks in Advance,
Shan

the question really needs to be directed towards the power score bible, as it is in their interest for their materials to be internally consistent, but I will say this: structure words such as "however", "therefore", "since", and perhaps "after all" are important to note, but they cannot replace using common sense. The word "therefore" is typically considered to signify "conclusion", but it is possible to construct an argument where it is used for a premise: "I woke up late, and was therefore late for the bus. My boss will kill me". My best piece of advise would be to take note when a structure word comes along, but make up your own mind what it is doing in each individual argument. The overall goal is to find the argument's bottom line - it's conclusion - the part that rests on, and is supported by the rest of the argument.