If he is used to taking 30mg IR doses, an Adderall
XR 60mg pill is equal to (more or less) two 30mg doses.
Some people like to take all of their stuff all at once, but with XRs I like to save half of it for the middle of the "trip."
Ideally XR releases half the doses within an hour then another one 4 hours later. I like to take the rest of the XR an hour before that second dose hits to extend and smooth the experience. Obviously, sleep will be difficult if you go that route, but I like to treat myself to an amphetamine
all nighter once a month. I also find that it's smoother that way.
If you take 40mg XR and then 20mg XR 3 hours later, it would be something like this.
after 1 hour: 20mg dose (1st 20mg of first dose)
After 4 hours: 30mg dose (2nd 20mg of first dose + 1st 10mg of second dose)
After 8 hours: 10mg dose (2nd 10mg of second dose)
This will give you time to test the water, and if you feel ok just being on 20mg, then awesome! You get to save the other 20mg for another day...
The last one kinda serves as a step down, instead of drastically jumping from 30mg to nothing.
I mean, if you don't mind crashing fast and hard, just take it all at once (provided your friend REALLY IS used to taking 30mg twice a day).
It's impossible to say whether it will be "safe" or not. There are so many different factors and so many things about your friend that we don't know. Blood pressure problems? Heart issues? Anxiety? Other medications?
There's a ton of info online about adverse side effects
and contraindications of Adderall. You should probably do a little research on your own as well. I mean, most people here, including myself, are not doctors, so really we can't tell you you are gonna be ok.