Each day those stocks that trade will either:
Rise in price - called Rises or Advances
Fall in price - called Falls or Declines
or their price will not change - called Steadies.
These three totals are used in the Advance - Decline indicator. There are some versions of this indicator which also need the steadies figure to get the total number of stocks that traded on the day.
Steadies have nothing to do with the New Highs - New Lows indicator.
A New High is a stock that traded on that day at a price higher than at any time in the previous year.
A New Low is a stock that traded on that day at a price lower than at any time in the previous year.
There is no equivalent for Steadies in the New Highs and New Lows data.