You're right, it looks like 700c is 622mm. My mistake.
------------------

[TABLE="class: grid, width: 728"]
[TR]
[TH]Decimal[/TH]
[TH]ISO[/TH]
[TH]Applications[/TH]
[/TR]
[TR]
[TD="align: justify"]29 inch[/TD]
[TD="align: justify"]622 mm[/TD]
[TD="align: justify"]This is a marketing term for wide 622 mm ("700c") tires.[/TD]
[/TR]
[TR]
[TD="align: justify"]28 x decimal[/TD]
[TD="align: justify"]Some German tire companies use this non-standard designation for 622 mm ("700c") tires.
[/TD]
[/TR]
[/TABLE]
[TABLE="class: grid, width: 728"]
[TR]
[TH]Fractional[/TH]
[TH]ISO[/TH]
[TH]Applications[/TH]
[/TR]
[TR]
[TD="align: justify"]29 inch[/TD]
[TD="align: justify"]622 mm[/TD]
[TD="align: justify"]This is a marketing term for wide 622 mm ("700c") tires.[/TD]
[/TR]
[TR]
[TD="align: justify"]28 x 1 1/2[/TD]
[TD="align: justify"]635 mm[/TD]
[TD="align: justify"]English, Dutch, Chinese, Indian Rod-brake roadsters
(Also marked F10, F25, 700 B)[/TD]
[/TR]
[TR]
[TD="align: justify"]622 mm[/TD]
[TD="align: justify"](F.13)Rare Canadian designation for the (F.13)[/TD]
[/TR]
[TR]
[TD="align: justify"]28 x 1 5/8 x
1 1/4[/TD]
[TD="align: justify"]Northern European designation for the 622 mm (700 C) size[/TD]
[/TR]
[/TABLE]
above via sheldon brown's site.