OK, gotcha. Reaper actually has a offset bar numbering feature which lets you adjust the bar 1 to any number you would want. It does come in handy when BIAB transfers a file over with a 2 bar lead in which is not present in the printed sheet music. I suspect other DAWs would have this.
Well Jimney Cricket and jumpin bull frogs . . . you do agree!!
I re-read my original post and don't see it as confusing, yet confusion emerged.
I can't speak to Reaper. If you reduce the tempo of the audio file by say 20% does Reaper still maintain the correct bar numbering automatically? In Studio One an adjustment needs to be made.