Is there a way to bypass the restriction within Android that volume doesn’t go above 25? I’ve looked in all the settings and can’t find anything. The max volume setting doesn’t increase the number above 25. I could do this on my Shield Pro.

turn the volume up on the device that you use for audio

The output of the box is variable (if you don't have max volume enabled).  0 to 25 is just the fraction of the MAX volume the box outputs.  As dishuser mentioned, if it is not loud enough for you, you should crank up the volume on your TV/Soundbar.   They could have numbered it from 1 to 100 and go up in increments of 4 instead and it would still be the same total volume output by the box.

I typically leave my TV at about 60% volume and then the 0 to 25 of the box is plenty.    Some people prefer max volume enabled, and then just use the volume control from thier TV/Receiver/Sound bar instead.  It's all personal preference.