Hi PP7BB,
For measuring high currents, you may not want to run them through such a device but use an external current sensor instead (possibly contacless). But AFAIK the GPM-8213 model does support external sensors.
The 'next' model, the GW INSTEK GPM-8310, does have two external inputs for external sensors and quite a high degree of adaptability to the characteristics of these sensors.
If measuring high currents is important to you, and doing so contactless is appealing to you, you may want to see whether you can still swap the device you purchased.
See also the below video for a detailled review of the GPM-8310: