Pivot and/or chart to group data by conditions

I'm pretty new to Pivots and Charting, have reviewed a bunch of sites online and videos but how to do this is just escaping me. I have the attached workbook to work with; the data tab is generally blank in the template, and the end user pastes the data they want to review; all other sheets should then calculate/update based on the new data.

They want to see the % of orders that took 20 days or longer to install, as well as those that took 10 days or less to install, delineated by month. The ability to see the % of middle ground (11-19 days) would be helpful as well.

I'm sure I could do this by writing formulas or editing data layout in other tabs and then creating a Pivot off of that - but isn't there a way to put a "condition" or a "formula" like "=Days_to_Installation>=20" within the Pivot itself?

Also, any suggestions for how to best chart this data to convey to the end user where their team stands in month-over-month performance at getting the orders installed in <20 days?

Thanks in advance. Hoping to learn more from this specific instance than I've been able to from others generic sample data sets.

David