If the Scale values are set to non zero values then this will scale the X-axis index to go with the corresponding Y Signal data values.

Fig.Plot(1..10).Index.Scaling.[Min|Max] = Numeric Value

Numeric Value:  Float (single)

Default:  0.0

Without any Index Scaling set the X-axis will simply be the data index.  

In this case the Y data has 50 data points.

Here we have set the Index Scaling from 1 to 2 and thus the X-axis is display below as shown

Index.Scaling.Min = 1

Index.Scaling.Max = 2