I assume you are meaning 250C and not 250C2 forks as well but i got both specs here.
I just checked my Cylmer manual (M371) and standard spec is 273ml with 268mm low level and 298ml high level for 250c
and 250c2 is 292ml std, 286ml low and 304ml high.
level range 250c - std 139mm - 114-144mm range
level range 250c2 - std 164mm - 144-174mm range
please note standard oil level on 250c2 with frame number 30643-35674 is 169mm
I don't think i have a DR manual though??
This thread probably would have been more suited to 'Suzuki' or 'Tech info' rather than 'general' so other people can find it while searching