This speccial dividend was required to be made under REIT rules. It resulted from merger and acquisition activity in the REIT investments held by RNP. This is a normal event every year and occurs in all closed end trusts of this type.
The dividend to which you refer is a special dividend not the standard monthly. I am not sure how they arrived at the amount but it would appear to be capital gains in the portfolio and unrelated to the monthly distribution or the regualr earnings on investments.