I guess that we are making it to complex :)

The SP you have according to the wallet of Busy or steem interface is used for the ranking. The SP calculate by steemworld is the one you are using when curating. For you this is 1956.25. This is based on 2356 own SP and 400.67 SP delegated out.
The 2356 own SP, is also shown in the wallet via busy or steem.
What I did mean to say it that the delegation is ignored. Both incoming and outgoing.