How is Sonic’s new strawberry mangonada slush only 110 calories for a medium?

A medium strawberry slush is 280 calories and a medium mango slush is 320 calories. Should I add those up and divide by Two or just use the 110 ?

A medium strawberry slush is 280 calories and a medium mango slush is 320 calories. Should I add those up and divide by Two or just use the 110 ?