Desk research against primary sources. Figures are traced to the issuing UAE authority and linked on the page.
The distinction that matters is between what a landlord may ask for and what a landlord can enforce. An increase notice is a proposal. The calculator's output is the benchmark the Rental Dispute Centre applies if the disagreement is actually heard, which is why an increase above it can be refused outright rather than negotiated down.
That makes evidence the practical part. Print the calculator result rather than relying on being able to reproduce it: the index behind it is refreshed annually, so a run made later may not return the figure your renewal was judged against. Put any refusal in writing as well — the Rental Dispute Centre works from documents, and an objection made verbally to a leasing agent leaves nothing to file.