This was really confusing initially for their interface, but the dotted line is the values you set and the solid line is the values it will actually be running at. For some reason it has built in scaling down by default, and it took me months to realize it was automatically halving my lighting settings the first time I set one up.
With that sort of configuration, your peak is only going to be with the T5s on, so your peak is 6 hours and everything else will be low enough by comparison that it won't count for a huge percentage of the total photoperiod (though it may be still be substantial directly under the lights).
While 6h of the t5s sounds reasonable enough to me, 8 hours of any light in my tank is just too short for me able to be to appreciate it as I like to, so while my peak photoperiod is around 7 hours (no t5s, just a single XR30), I have a long ramp up and down on both sides where the tank is lit, but where the photosynthetic activity isn't all that much (and many corals start shrinking up more than an hour from moonlights as a result), with light present for about 12-13 hours and another hour or two of moonlights depending on the automatic moon cycle settings.
Also worth mentioning: unless your T5s are pretty blue, that will look very white for a lot of the day if your XR15s are Pros and not Blues. On the Pro model of the fixtures, much more of the total output power is in the whites than some fixtures, so the settings with the blues at 50% and the whites at 100% is probably going to be a warmer thank 10k Kelvin sort of look on their own.
LED spectrum counts, but a good fixture will cover enough of it not to make gigantic differences in health or growth - much more likely to see differences in coloration, especially in non-fluorescent colors (like on fish or some corals). Remember that the quantity of actual LEDs of each color is chosen by the manufacturer, so at least in theory, setting everything across the board to the same level will give you a pretty good blend. In practice, people don't usually do this and I don't think it looks the best or photographs the best, but having something on for each channel helps cover the bases. I also do a similar thing with my lighting schedule where the spectrum is warmer (more whites/reds/greens) early in the day and then more blue in the evening, so you get to appreciate the variation you get from different looks and so that you are actually running each channel somewhat comparably in total during the day. My vote would be to chose color spectrums that look good to you and use at least most of the channels in some amount, then rely on PAR to get the right output level.
