The number of supported routes in the ASR 1000 seriesis determined by the combination of both the RP and the ESP. When the system has an RP1 + ESP5, the limit is 500k (because of the ESP5).
When the system runs an RP1 + ESP10, the limit is 1 million routes (both RP1 and ESP10 reach the limit).

Subsequently, you can upgrade ESP5 to ESP10 on ASR1002 to increase the route scale from 500k to 1M.