That's an expected loss for an ozonator that is on all the time -- it can actually be higher than that. There is probably no reason to have the circulation pump running 24/7. If you cut that back to running half the time in shifts, say 2 hours on 2 hours off or something like that, then you should lose less chlorine. It doesn't sound like you've got any unusual chlorine demand such as from biofilms.
There's no way the ozone is at 250 ppm in the bulk water nor in the circulation flow entering the spa. They might mean that is the concentration in some side stream, but without knowing the fraction in the side stream it's hard to know how quickly the chlorine will get used up. Or perhaps that is the air concentration of ozone, but without knowing the efficiency of injection into the water it is again hard to know. At 30ºC (86ºF), a 1% CD unit could have no more than 2.7 ppm ozone in the water. If their 250 ppm is air concentration, then that is only 0.025% so would result in around 0.068 ppm ozone in the water which sounds about right. If that all eventually reacted with chlorine (in practice, some breaks down into hydroxyl radicals) and if the turnover rate was 30 minutes for the circulation pump, then that is 0.068*70.91/48 = 0.10 ppm chlorine or 0.2 ppm per hour or 4.8 ppm per hour or around half your chlorine demand. Seems to all add up even with the gross assumptions I've made.
There's no way the ozone is at 250 ppm in the bulk water nor in the circulation flow entering the spa. They might mean that is the concentration in some side stream, but without knowing the fraction in the side stream it's hard to know how quickly the chlorine will get used up. Or perhaps that is the air concentration of ozone, but without knowing the efficiency of injection into the water it is again hard to know. At 30ºC (86ºF), a 1% CD unit could have no more than 2.7 ppm ozone in the water. If their 250 ppm is air concentration, then that is only 0.025% so would result in around 0.068 ppm ozone in the water which sounds about right. If that all eventually reacted with chlorine (in practice, some breaks down into hydroxyl radicals) and if the turnover rate was 30 minutes for the circulation pump, then that is 0.068*70.91/48 = 0.10 ppm chlorine or 0.2 ppm per hour or 4.8 ppm per hour or around half your chlorine demand. Seems to all add up even with the gross assumptions I've made.