For reference, you can see how the decoder is plucking numbers out of the offer details and calculating values as I kept this simple javascript on the page. View source or read it here:
https://github.com/itsanalogue/bmwle...ndex.html#L143
If you are not getting the correct MF for your specific deal, then I suspect you have additional fees being amortized into your monthly payments above depreciation and rent. You'll have to figure out where they are adding costs since the published BMW offer only accounts for depreciation and rent, which for your numbers would land a $1399/mo payment before taxes.
So find out what is causing the extra $153.50/mo. It might be government fees, they could be adding inflated dealer fees, or <gasp> scotchguard for your seats
.