Mac mini 2018- Reset to factory settings, and "virtual" hard drive.

Hello everyone

Recently I bought an used Mac mini 2018 on eBay. It came with OSmonterey, I noticed that the web surfing was really slow compared to my older PC desktop, both through ethernet and wi-fi, despite the speed test was ok. I read on internet that since Monterey is optimised for M1, some people with older intel Macs experienced lags and slowdowns. So I decided to do a reset to factory settings, in my case OSmojave, and it really worked out! Now Internet is really snappy, no more slowdowns (despite the speedtest result is the same as before....yes really weird but it worked).

To do the reset to factory settings I followed a couple of videos on youtube (see the screenshots), I restarted the Mac holding CMD+SHIFT+OPT+R.

During the reset...in the disk utility panel I saw another kind of "virtual HD" (same size of 250gb of the main HD) called UPDATE that was ejectable, but I didn't eject it, because in the tutorial of zollotech-see screenshot- the guy didn't do it.

But now I have a sort of virtual drive in the Mac, that I don't know what I have to do with.

If I eject it what happens? Does it have anything to do with the previous OSmonterey?

I should eject it during the reset?

In the screenshot you can see the content of the HD.

I want to get rid of it: but I don't want to make damages.

I had a macbook long time ago: but I never did these reset stuff.

Thanks in advance

S.