Charting doubt_1

Dear Experts,

                    I have an issue like below, so in the Worksheet "SssgSwitchEvaluation_Study_curr",

I want to make a graph like below with the Variables, Time, CurrentState, slot and Time(ms) as below

But problem is that at 504 like below we know that the current state is changed to sparse(from dense), but how to shown that in a Graph? when it's non-numeric(I must say I did that earlier and some times it worked, not sure what's changed now)? also the slot I tried as Secondary axis, but not sure what mistake I am doing, it shows a straight line..(slot can range from 0~19), Attaching the worksheet. :-

Thanks in Advance,

Br,

Anupam