It's interesting that for both trials, the rain validator's water evaporates at a faster rate for the first day and then it's rate becomes increasingly slower than that of the beaker. The beaker has a larger radius, so this is likely due to a combination of the saturated wick having more surface area and a smaller percentage of the validator's total mass remaining over time compared to the beaker. This can be seen in the right two graphs in the first picture: the beaker's percent mass decreases more linearly than the validator's, which has a slight upward concavity.
Some errors with these trials include the changing humidity of the environment as well as the temperature of the room, especially since the beaker and validator were set near an oven that ran at varying temperatures for varying amounts of time. Because the beaker's and validator's locations were constant and adjacent, the validator's performance can accurately be compared to that of a plain, 1L beaker of water.