Singapore Citizenship AIP (Approve in principle)

Applied Singapore citizenship on June 2014, it took more than 10 months for ICA to process my application,  24th April, I opened my mailbox as regular, found one letter from ICA, it was one page and I thought it was a reject letter, normally one page letter is always rejection letter, but when I saw ‘We are pleased to inform you  that…’, it was approved, the date is 19th April, took one week to reach my mailbox.