Yes I'm pretty sure he means Seven Eleven.
Last year he was kind enough to write us all out a list of his fast food restaurant slangs! XD (translated by Meredith)

McDonald's → MakuDo
Moss Burger → Moss
Kentucky → If not Kentucky then KenChickie
Mister Donut → MisuDoh
SevenEleven → Seven
Family Mart → FamiMa
ampm → AP
Yoshinoya → YoshiGyuu
Tenkaippin → TenIchi
Don Quixote → DonQui
Inari Sushi → O-Inari-san