Miro or MRO stands for 'Mass in Running Order' and is the unladen of your caravan with standard spec, as it leaves the factory. Go-Pods are just 480Kg.
MTPLM stands for the 'Maximum Technically Permitted Laden Mass', (750Kg on a Go-Pod), and this figure should not be exceeded. Although with the Go-Pod's generous 750Kg allowance, you'd be hard pushed to overload.
The MTPLM must not be greater than the towing car's Maximum Permissible Towing Mass (MPTW) which is defined by the car manufacturer and found in the cars manual.