Absolutely! You are the professional and your judgement is paramount to the process. If you rely on a source for market rate that you believe is superior OR believe a different figure is more prudent, simply enter the ANNUAL rate you find most reliable and click save. All properties will be adjusted from the contract dates to the effective date on a straight line basis, unless contracted within the window of unadjusted days provided by you.
See the knowledgebase article Understanding Market Rate Changes for more detail.