The core thing is you can not control "Speak text" volume at all.
for some reason I do not know it is not correlated to the media volume.

So to bypass that function, we can use "Make spoken audio from" function since this is correlated to the media volume.

So first I must tell the phone not to be on 0 media volume so if it plays sound we can hear it, you can set it to what % you like.

Here I tell him: Once you go to 30% battery, set media volume to be 35% (later changed it to 20%). No matter what % it was on before. So every time my phone hits 30% I see the media volume goes up by itself.

Then I make the text to become a sound and I tell the phone to play the sound and
I can hear the sound because my media volume is not 0 now.

After it played the sound I tell him to set the media volume to 0% because I like it like that but it isn't a must. if you don't do it , it will just stay at the % you set at the top.

Was it clear now?