Rc describes the thermal resistance of a building construction. It is different from the property of one insulation material considered alone. A comparison needs to identify the assembly and assumptions associated with the stated figure.
How this term relates to your project
Quotations sometimes mix material properties with construction values. Ask what each figure represents and which layers are included. A higher resistance means greater resistance to heat flow within that comparison, but does not describe every junction or the performance of the whole house. Thermal bridges, airtightness and ventilation remain separate considerations.
Use the value to compare equivalent building components on consistent assumptions. A generic regulatory threshold found online does not replace identifying requirements for your project. Keep the chosen assembly and its supporting information together so later decisions are not based on a number detached from the construction it originally described.