Extrapolating Missing Data

I took the liberty of doing what MrShorty suggested and the result is that a third-degree polynomial is a perfect fit for your existing data. Attached is a file that plots your points on a scatter graph. I tried various fits and the one shown has an R² of 1, which is perfect (0 is no fit). The equation is shown on the chart. You can use that equation, where x is the Level, to give you the number of points for that level (y).

The short answer to your question is Excel does not do interpolation* automatically by dragging values but it gives you enough tools to do it yourself.

*Interpolation is filling in gaps within the known range of data, which is what we have here; extrapolation is extending your data outside the range for which actual data exists.