According to Kodak:(posted 8677 days ago)"You can dilute KODAK XTOL Developer 1:1, 1:2, or 1:3 with water (developer:water) for one-shot (single-use) processing. Dilution at 1:1 will provide slightly greater film speed, enhanced sharpness and shadow detail, and slightly more grain. Dilution at 1:3 will generally provide less film speed and shadow detail, with enhanced sharpness and slightly more grain."
Also, Kodak suggests a minimum of 100ml stock XTOL per 36 exposure roll. Since your tank requires 850ml, you will meet that requirement at dilutions of all dilutions above, including 1:3.
I suggest you try 1:1 and compare to your results at 1:3.