Past-Level is usually shortened to Past.
A Past-Level states a historical numeric Level, on a defined Quantification-Scale, under specified Conditions [time, place, event] for a Scalar Attribute.
The Past can be any reference point of interest. It can be used to express a Product-Function, Product-Value Level, Development-Resource, or Solution of an old or existing system.
The most common use of the Past-Level is to reference how well a previous Product did along the same Quantification-Scale.
It can be essential to know where along the Quantification-Scale we and our Stakeholders are (Past-Level), Before we decide where we want to be in the future (Goal-Level). Specifying the Past Level gives that Benchmark and communicates it clearly. The Pest-Level is not a Requirement in-itself, it can be part of describing the development challenge, to move from where we are, the Past-Level, to where we want to be, the Goal-Level.