**Brightness Calculation Question**

I have a pretty large disparity in measuring how bright my projector is and I am hoping for some input.

using a 100% pattern:

If I measure using an i1pro I get 11.5 FtL calibrated.

Using a LX1330B Lux meter, I get close to 200 Lux. I am using the LuxtoLumens excel sheet someone here posted, and I have also done the math manually. I get 551 Lumens/20.4 FtL.

That is a big difference and I am not sure which to trust (if either)

The screen is supposed to be 1.1 gain and I have a 144" throw.