Lump Sum in Arrears Payment Tax Offset

[#1]

Hi, can anyone please direct me to where I can find the calculations the ATO uses to work out what a Lump Sum in Arrears Payment Tax Offset should be? I have determined that my LSIAP meet all eligibility requirements. I would however like to know how this is worked out so I can check if the amount the ATO has come to is actually correct.  Without knowing the formula used, it is really impossible to determine whether a figure is correct or not to allow for an objection. Thanks in advance, hoping someone can help. 

[#2]

I found the calculation in the Income Tax Assessment Act 1936 at the following link from the ATO website. It is a little hard to understand to be honest. Lots of googling coming up  

https://www.ato.gov.au/law/view/document?DocID=PAC%2F19360027%2F159ZRD&PiT=**TFN removed**35958