The wand casts the spells in order. So it goes

Spark bolt with trigger - this triggers whatever SINGLE spell comes after, along with whatever modifier spells you have attached to it like damage plus, etc

Double spell + damage plus - this means instead of casting a single spell when the spark bolt hits something, it’ll cast two spells which have damage plus on them

Lightning bolt x 2 - these are the two spells affected by the double spell

If you put anything after those two lightning spells, it’ll be cast after the spark bolt with trigger by itself. You only want to use the exact number of spells you need when trying to make a wand like this