Split Slot is sort of like Echoing Spell, but usually better(*): Echoing Spell uses up a spell slot 3 levels higher (instead of 2) relative to the original spell, and only lets you cast the same spell again, whereas Split Slot effectively acts like Echoing Spell with only a +2 cost, but also adding the option to prepare 2 different spells (although they must be the same level as each other unless you waste some of the potential for one of them). So by way of analogy to the example given in the Split Slot description, it never reduces the level of a spell, but instead lets you prepare 2 2nd level spells in a 4th level slot. Note that at these low levels it isn't very good -- it gets better when you get to higher levels, so that the fractional level drop is less (although the non-linear increase in the power of spells of higher levels offsets this to some degree).
(*)Certain Metamagic cost reducer feats and traits can reduce or even eliminate the cost of Echoing Spell, but just for 1 spell. Metamagic Rods of Echoing Spell could work for up to 3 spells each, but cost lots of money to get. Split Slot, on the other hand, has no direct interaction with Metamagic cost reducers, since it isn't actually Metamagic.