Archera Guaranteed Reserved Instances (GRIs) have two variable components, a term length and a Premium, that are inversely related. The longer the term length, the lower the premium, and vice versa - shorter term lengths have higher premiums. The GRI Premium is the difference between the standard Savings Rate of the underlying standard RI/SP, and the net savings rate of the GRI. You can see the GRI premiums on your invoice page.
Keep in mind, GRI premiums are only assessed on realized savings. Meaning - if for some reason you can't use the underlying infrastructure, you aren't responsible for the premium.