You can set Ticksize in information window of AB. In preferences > intrayday settings of AB you can set 5 custom range bar sizes.
When using Forex and e.g EURUSD then Ticksize is 0.0001 so I need to set Ticksize to 0.0001 in EURUSD. If setting range bar size to 8R then bar goes from e.g 1.3000 to 1.3008. If Price goes to 1.30081 or to 1.3009 then new range bar is drawn. If price goes to 1.3008 then no new range bar is drawn. And that's what it's doing in 5.50.