I don't think the formula given on paper test can be applied to the actual computer based test or to a test with only 78 questions (37 Quant and 41 Verbal). This is beacuse paper based test always has around 6/7 sections with a total of 106/108 questions and the RAW score that you get out in that 108 questions can tell you your actual score in GMAT based on the table.
However, if you have only 78 questions as you have in a CAT, you can never get a RAW score of more than 78, which as per the paper based test score conversion table, this score means an actual GMAT score of only 620. So, paper conversion table cannot be used to get actual GMAT score unless it tells you that the RAW score of 78 means 800, then you can find out.
Milind
