Need formula for different rates of completion to be used to calculate rental revenues

I am working on a financial model for a commercial real estate development. I have created the timeline and an assumption for when the first units will be available. What I need is formula for rate of completion, as in "fast, medium, slow" where fast would be something like 30 units in first month, 50 in second, 70 in third, up to 318 and slow would be more like 10 units first month, 15 in second, etc. Our average SF / unit is 980 and average rent is 1.55/SF so I need to use those figures and the rate of completion schedule to have a projected rental revenue figure for each month starting with the month the first unit is available.

I hope that my question is somewhat clear. Thank you for any help