If you bought an inexpensive bow, was it new or used? Where is the center of the bow? When you measured the tiller, did you measure the upper and lower limbs when strung, perpendicular to the string at the fadeout of each limb?
Assuming the center is below the arrow shelf, around 1.5" below the arrow shelf, the tiller of the upper limb might be 3/16" to 1/4" greater than the lower limb, because the lower limb is shorter and therefore stiffer. If this is what you find, I think it is normal and what you could do is experiment with the length of string. Assuming the string is correct for the bow, take the twist out and shoot a few arrows, increasing the twist, about 5x in the same direction you found it when it was purchased. Assuming you know the manufacturer, check online to see if they have a recommended brace height. Your knocking point might be around 1/4" above perpendicular from the string to the arrow rest. Experiment with the brace height and knocking point to get the best flight.
There are other factors that affect arrow flight, and I am assuming the arrows are a good match for the bow.