Valencia found the net only once last term having inherited the number made so famous by George Best, Bryan Robson, David Beckham, Eric Cantona and Cristiano Ronaldo.
The Ecuador wide-man requested a return to the 25 shirt this summer, and manager Moyes was happy to oblige.
Now, having seen Valencia drive home United's fourth in their 4-2 Champions League win over Bayer Leverkusen on Tuesday, Moyes has set the former Wigan man an eight-goal target this term, two more than his best return, achieved in both 2010 and 2012.
"They kept telling me he needed to change his number, so we got it changed for him," said Moyes.
"Sometimes, psychologically, it can make a difference to a player.
"Overall, I've been really pleased with him.
"I actually said to him today [Friday] 'you should be getting yourself seven or eight goals a season regularly'."
For someone who first arrived in England in 2007, Valencia has made very little progress learning the language.
But Moyes this he got the message.
"Antonio looked at me and squinted a bit," he said.
"He only scored one last season but he's got off to a good start and hopefully he'll get close to the target I'd like to him get this year."