Note this particular flavor of Lua is
Havok Script that unfortunately uses the default C library not so random "rand()" function (default for a windows Lua build) at it's core.
It only has 15bits precision and has pretty bad pseudorandom properties.
It's too bad they didn't implement a nice 53bit RNG like LuaJit now has.
At any rate if you want a better RNG you might code one in pure Lua. Just keep in mind this Lua version uses doubles (64bit floats).