Cell Calculation

Hi I am trying to quantify how our models are growing by building a calculator. I have just found the space calculator in the agile implementation app which looks excellent and will save me some time! However - I cannot reconcile the results of the calculator to the cell count listed against my existing model in Anaplan. I am sure I am missing something or has anyone else come up against this? Using one example where I have a module with the following attributes:

• 10 line items
• 1 list dimension (33,311 items as quoted in the general list screen which includes summaries) 
• 5 versions
• Time by month (4 future years and 1 past year plus current year is 6 years plus totals gets you to 79 months)

So the calculation should be as straight forward as 10*33,311*5*79 = 131,578,450. The app seems to agree with me. But my module thinks it has 108,306,980 cells. I could deduct 392,630 cells from my total by allowing for the fact that one line item has the summary property to only aggregate on time and not on the list summary but that still gives me a 21% difference to the stated cell count. I am certainly not complaining that my module is taking up less space than I think it should be, I would just like to understand if there is some complexity that I am unaware of when estimating space!  Any thoughts? Regards Kirsty