stroke-dashoffset

html,body,svg { height:100% }

<svg viewBox="-3 0 33 10" xmlns="http://www.w3.org/2000/svg">
  <!-- No dash array -->
  <line x1="0" y1="1" x2="30" y2="1" stroke="black" />

  <!-- No dash offset -->
  <line x1="0" y1="3" x2="30" y2="3" stroke="black"
        stroke-dasharray="3 1" />

  <!--
  The start of the dash array computation
  is pulled by 3 user units
  -->
  <line x1="0" y1="5" x2="30" y2="5" stroke="black"
        stroke-dasharray="3 1"
        stroke-dashoffset="3" />

  <!--
  The start of the dash array computation
  is pushed by 3 user units
  -->
  <line x1="0" y1="7" x2="30" y2="7" stroke="black"
        stroke-dasharray="3 1"
        stroke-dashoffset="-3" />

  <!--
  The start of the dash array computation
  is pulled by 1 user units which ends up
  in the same rendering as the previous example
  -->
  <line x1="0" y1="9" x2="30" y2="9" stroke="black"
        stroke-dasharray="3 1"
        stroke-dashoffset="1" />

  <!--
  the following red lines highlight the
  offset of the dash array for each line
  -->
  <path d="M0,5 h-3 M0,7 h3 M0,9 h-1" stroke="rgba(255,0,0,.5)" />
</svg>