3.3.5.2 Inventory Ordering Module Formulas - Shipping Method

Hi everyone, I appreciate any help that can be provided, I was very stuck on the formula for Shipping Method.

I was trying the formula below and getting error "Format of mapping used for lookup doesn't match any dimension of the source". I believe I am using the correct module line items, but am struggling to understand why they are not giving the correct result.

'SYS07 Distribution Center Details'.Default Shipping[LOOKUP: 'SYS08 SKU Details'.Product, LOOKUP: 'SYS08 SKU Details'.Distribution Center]

EDIT:

I found the linked that I copied below that explained  that I only need one LOOKUP to the SYS08 Distribution Center and that the final formula is 'SYS07 Distribution Center Details'.Default Shipping[LOOKUP: 'SYS08 SKU Details'.Distribution Center]

https://community.anaplan.com/t5/Anaplan-Platform/3-3-5-Shipping-Time/m-p/129029#M32812

I am still not entirely understanding why only one LOOKUP is needed when we want to look at both Distribution Center and Product SKU as criteria to determine the Shipping Method. I am assuming that it is because both the Distribution Center and P3 SKU list are in SYS08, but I am not understanding why you don't need to point the LOOKUPs to both the Distribution Center and the SKU?

Thanks again for any help, I really appreciate it!