I assume you are talking about engineering drawings created to MIL-DTL-31000. To diverge a little, most commercial non-DOD organizations do whatever works for them in regards to engineering drawing numbering.
Yes, for milspec engineering drawings the dash numbering system starts -1 then increments in odd numbers, i.e. -3, -5, -7, 9, etc. A left side or opposite component is numbered sequential and as an even dash. So, for an opposite side part (Starboard as opposed to Port) of a -3 would be a -4.
For those of you whom have never heard of this, it make sense in the aircraft world where we have parts/components that are true mirror images, particularly in the wing or airfoils.