The plate-loaded seated calf raise machine positions your knees bent at roughly 90 degrees, which shifts more of the load onto the soleus muscle underneath the calf compared to a standing calf raise. It is a common finisher for calf training because the seated position also removes momentum from the hips, making it harder to cheat the movement.
Log your lever seated calf raise plate loaded sets in 1RM.fit and watch your estimated 1RM update automatically as you get stronger.