They let you set the spiciness level on a scale of 1-5 (larger number, more spice). If you like spicy, 3 will make your lips tingle & your nose run while 5 has you sucking air and your face sweating.
Never eaten at Gurkhas physically, but their delivery is prompt & the food won't disappoint. I ordered it about 3x in 2 weeks because I like it so much. I highly recommend it if you're craving Indian.