Donald Trump said to Puerto Rican officials that they should be proud that more Americans didn't die from Hurricane Maria. He then compared Hurricane Maria to Hurricane Katrina, something which Trump termed a 'real catastrophe', a term that he did not use for Hurricane Maria's devastation. By making this distinction, Trump is implying that Hurricane Maria was not a 'real catastrophe', at least in his mind that is.
Trump used the official death count as a type of macabre scorecard for his administration's performance. Since the official death count is much lower than Hurricane Katrina's (something he called a 'real catastrophe') he believes that he's worthy of praise. Tellingly, he fails to see the dead as individuals. He sees the official number of dead as a buttress against complaints of his administration's incompetence.