Reduce range of slider

I have my tv found as dlna. Its only available function seems to be to control the volume. The volume in the TV goes from one to 100 but the only usable range is about 10-30. Anything above 30 is way too loud.

I’m currently using.
type: custom:slider-entity-row
entity: media_player.bedroom_tv

It’s not very useful in the UI because you can only jump. In increments of five. Meaning I would only ever use the values 15 and 20. Is there any way of making a slider that only goes from zero to 30?

I thought about making a helper object and then using some automation. To copy the values over but. I’m sure there must be some better way.