Need different symbol charging means

[doistons]

Hi, people! I have a trouble with charging my phone: It's a Asus Zenfone Max Pro M2, Android 9.0
When I'm charging with original charger, appears this symbol

And I don't know what it means. I hope that someone may help.
When I use other charges, this symbol don't appears. I have a cousin with the same phone, I used his charger and the symbol appears too.
I did the factory reset and the problem continue.

[BlueHunt]

That plus sign with red color is indeed a great feature which denotes that your device is charging "Rapidly" and that plus sign usually stays red until 70-75% until which your phone keeps charging itself rapidly, then till 100% that plus sign becomes normal black colored and that time the phone charges itself in normal speed and once that plus sign disappears, that means your charge is either complete (at 100%) or you have disconnected your charging cable during charging.

[Y_ASUS]

Hi doistons,
What is your battery level when the + sign turns red? Does the "+" appear red no matter which battery level?
Could you tell us your current firmware version? (Settings > System > About phone > Build number)
Thank you 🙂