A rich man was found murdered one morning

the police had identified three suspects, all of them had motive and an opportunity to kill him

their names are oliver, jason, and adam

all of them claimed that they didn't do it, but jason and adam seemed nervous during interrogation

police found a note left behind by the victim

moments before death somehow the victim was able to write some numbers on the calendar with his blood

"1 4 9 10 11"

what does the victim want to say through numbers?