PD mode decode results in short images

[nivex]

When decoding a PD image (in my case PD180) I get a roughly half height image:

Something I can't get my head around in the math:
The spec says "COLOR SCAN TIMES (Y, R-Y, B-Y)" for PD180 is 183.04ms.
183.04 / 640 = 0.286, as you have listed in modespec.c
/but/
the spec then says the sequence is Y(odd), R-Y, B-Y, Y(even). Wouldn't that mean there's a whole extra line not being accounted for somewhere?