Question related to ROHC-TCP Profile

Hi,

I've just started working on implementation of the ROHC-TCP profile,
and I needed some clarifications.

Question about "seq_number_scaled" field defined in the CONTROL format
of the tcp(payload_size, ack_stride_value, ip_inner_ecn) encoding
method.  It is defined as:

CONTROL {
     seq_number_scaled                    [ 32 ];
     ...
   }

and isn't appeared in other formats.  If I truly understood ROCH-FN,
this definition specifies only ULENGTH attribute of this field, so the
question is: where compressor can get its UVALUE?  And the second
question is how decompressor can restore it?

Thanks in advance,
Igor.