Lennox - Model Number differences?

Hi, I'm trying to understand the difference between the following model numbers for a Lennox 2 stage heater

el280uh090xe48b vs el280uh090xp48b

I found a site that points out the highlighted letter is for info about the blower. P = PSC Multi-Speed Blower Motor. What does "e" mean?

Thanks!

source https://hvac-talk.com/vbb/showthread.php?2223754-Lennox-Model-Number-differences&goto=newpost