A panelboard does not have an IR (interrupting rating) as it really can't interrupt any current. A panel/panelboard/switchboard/switchgear have an SCCR (short circuit current rating). This relates to how the panel and busbar is made so that it physically withstands the magnetic forces of a short circuit current.
I would say that the panelboard you are looking at can be purchased in a range of SCCR's from 14-100kA. You need to know what the fault current is at the location this panelboard will be installed to spec the required SCCR. Of course the price goes up as the SCCR increases.
