How much credit is the utility company supposed to give?

I just got my first bill with my panels plugged in. According to the bill I'm getting credit for each produced excess KVH at the rate of only %62 of what they charge me for each KVH I use from them. Is that normal? I'm in Texas. Also do I understand it correctly, that what this means it's cheaper for me to use the electricity during the day than at night, because each KVH drawn at night comes from the grid?