See Sandisk SATA SSD Plus 240GB Smart values - #5 by ProtopiaUK
I have the same problem with my new Sandisk Plus 240GB SSD - after 3 weeks of almost continuous power on, it was showing 22 hours power-on time.
Assuming that your drive accumulates power-on-hours at the same rate mine did, it sounds like your SSD wasn’t new when you bought it and at a guess might have been previously used for c. 4 months.
