Prism 7 lets you enter data with 13-14 digits for each value (double precision). In contrast, Prism 6 allowed to to enter only 6-7 digits (single precision).
Allowing more digits prevents round off errors when importing or pasting data with more than 6 or 7 digits of precision.
Additionally, all calculations now use doubles instead of integers. This allows Prism to avoid integer overflow and as a results work better with large data sets (large N). Prism already use double-precision floating point math.