Lambert wore his new number for the first time during a 45-minute run-out in Saturday's 2-1 friendly win at Preston North End, and afterwards told Liverpool's official website how much it meant to him.
"It's a great number for me to wear for Liverpool, I've always seen myself as a number nine as it's the type of player I am, and to get it at Liverpool is unbelievable," he said.
"I would have been happy with any number because as long as that badge is on the front I would have been happy with any shirt, but to get number nine is special for me."
Lambert became Brendan Rodgers's first signing of the summer when he joined from Southampton, and he admitted to some pre-match jitters in the Deepdale dressing room as he readied himself for his first appearance for his boyhood club.
He added: "It was special. I had to get a few moments in check at the beginning, but it was special. I was a little bit disappointed not to get a goal but I thoroughly enjoyed it."
Liverpool's Premier League campaign begins on August 17 when they host Lambert's former club Southampton.