Trying to flash just the calibration from my base file into the pcm after I loaded the initial cos 5 file and it won't let me flash the new calibration. It says that the os's have different numbers.

99 chevy c1500 5.3. I built a file from an 02 file downloaded from tunefiledepot flashed the cal and os and got it running just fine. sucked out the new file and saved it. shut it off, flashed the cos 5 base file 02020003 and it went well. Now it is stuck without a calibration because I am trying to follow step 4 which says to flash just the calibration from the file I read after it was running good and it gives an error that the os have different numbers and that it won't allow it to calibrate.

"Open the *.tun file that you saved in step 1. It contains the PCM’s calibrations from before the EFILive Custom Operating System was installed. Perform a calibration only reflash of that *.tun file.
At this stage, the PCM is capable of starting and running your engine. However, don't get too excited just yet, there are a few more steps that must be completed."

What am I doing wrong?