Using wizard - what does it do if "ActiveStepIndex" is NOT set to 0, in the .aspx file?

HI,
I'm working on an existing web forms app, where 1 .aspx page uses wizard, and has the following code:
<asp:Wizard ID="wzSubscribe" runat="server" ActiveStepIndex="3" OnFinishButtonClick="wzSubscribe_FinishButtonClick" OnActiveStepChanged="wzSubscribe_ActiveStepChanged" >
       <WizardSteps>
            ......
Note: This wizard has 6 steps altogether. I'm not sure why the previous developer set the ActiveStepIndex="3"? This code works in PROD, and when you run the app, it does not go to the 4th step (where ActiveStepIndex is 3) directly, but still goes to 1st step (where ActiveStepIndex is 0).
SO is this code wrong? Or does it matter what number I put here?
I don't understand what does ...