I think he meant just that. Though, as i see it.
Squad:
DDG. NOT homegrown
Romero NOT homegrown
Johnstone Homegrown
Smalling Homegrown
Blind NOT homegrown
Rojo NOT homegrown
Jones Homegrown
Bailly NOT homegrown
McNair Homegrown
Blackett Homegrown
Shaw U21, but turning 21 in July, Homegrown
CBJ U21
Darmian NOT homegrown
Valencia NOT homegrown
Varela NOT homegrown
Schneiderlin NOT homegrown
Carrick Homegrown
TFM U21
Herrera NOT homegrown
Fellaini NOT homegrown
Schweinsteiger NOT homegrown
Mata NOT homegrown
(Mkhitaryan NOT homegrown)
Pereira U21(Turning 21 in January, becoming homegrown)
Depay NOT homegrown
Young Homegrown
Januzaj Homegrown
Lingard Homegrown
Rooney Homegrown
Martial Homegrown
Ibrahimovic NOT homegrown
Rashford U21
Wilson U21 (Turning 21 December 1st, becoming homegrown)
Keane Homegrown
Homegrown: 12
U21 becoming Homegrown during/before season: 3
U21: 3
NOT homegrown: 16
Total in need of registration (over 21): 31
This means at least 6 of current squad (including Mkhitaryan), can not be registered. Of course players like Pereira doesn't need to be registered until January, so that can be "fixed" at that time. Some of the mentioned can/will be loaned out or sold, likely players like Blackett, Keane and possibly Wilson. Still, we will need to get rid of some players, which will undoubtedly happen, with Mata, Rojo and Darmian being linked away.
This at least means we'll definately see some players moved on before the end of August.
PS: Sorry about the colors, just wanted to make it understandable