So i'm playing with my 486 build and after some weird crash just after wolfenstein 3d was started (sound crippled and then the system hanged), after some troubleshooting with config.sys and autoexec.bat to be sure it was my fault.
I changed my config.sys file from emm386 to jemmex, then the system worked like a charme.
Then I noticed a weird thing (since i'm still on configuring stuff so I frequently reboot, with the very same autoexec.bat and config.sys, same bios options (I neither entered in it), here is what happened:

First reboot:
Jemm v5.83 [12/04/22]
System memory found at c100-c7ff, region might be in use
System memory found at e000-ffff, region might be in use
[..]

Second reboot:
Jemm v5.83 [12/04/22]
System memory found at c100-c7ff, region might be in use
System memory found at e000-f3ff, region might be in use
System memory found at f400-ffff, region might be in use
[..]

Doing some simple mat here is what I found:
First reboot: FFFF-E000= 1FFF (dec 8191)

Second reboot:
F3FF-E000= 13FF (dec 5119)
FFFF-F400= BFF (dec 3071)
13FF+BFF= 1FFE (dec 8190)

So there is a difference of 1 bit\byte (I don't know which one) between those 2 results.
Is it normal a normal behaviour?
Any guess?