Custom DOE - factor levels

[#1]

I want to create a custom DOE.  I have 1 discrete numeric vatiable with 3 levels (1,2,3).  I have 2 covariate factors.  I also has 1 continuous variable.  The problem is I want the DOE with 5 levels for the continuous factor and JMP is only allowing me 2 levels.  Am I doing something wrong when I specify the continuous variable or am I limited to just 2 levels?

[#2]

Use the discrete numeric factor to define a continuous factor with pre-determined levels. It will be modeled with continuous fixed effects. The algorithm requires up to a fourth-order term to work but the estimability will be set to 'if possible.' Just leave all that alone.

[#3]

To expand on Mark's answer, a continuous variable will have the number of levels chosen to estimate your given model. If you only specify a linear term for your continuous variable, then you only need two levels to estimate that term. Any more terms would not be as efficient and less than optimal. You use Discrete Numeric whenever you want to force certain levels of a continuous factor.