Used variables:

• X: the value of the input
• X1, X2: the nearest points in the lookup-table (input-values of the lookup-table)
• Y1: the output of the lookup-table when the input is X1
• Y2: the output of the lookup-table when the input is X2
• DX: distance between X2 and X1, is always 10, DX = 10
• DY: distance between Y2 and Y1, DY = Y2 - Y1
• dx: distance between X and X1, dx = X - X1
• dy: distance between Y and Y1, dy = Y - Y1

Linear interpolation:

• DX/DY = dx/dy
• so dy = dx * DY / DX
• as dy = Y - Y1 and DX = 10, this results in
• Y - Y1 = dx * DY / 10
• so Y = dx * DY / 10 + Y1 

On the figure shown above is the interpolation schematic in the Realizer simulator. As you can see on the table on top the X is already known that is 15.

• On 15 seconds the interpolation calculats that the Y must be 226.
• 226 is where the two lines cross.
• One step back is 14 with output 196 and one step forward is 15 with output 130.