Temporary data:

If any portion of the volume number/sequential designation (subfield $v) information is subject to change (e.g., when the record for a multipart item is not yet complete), angle brackets ( <...> ) are customarily used to record that part of the volume number/sequential designation information which is subject to change. As parts are added, the information is updated. Three spaces precede the closing angle bracket.

Example:

440 #0$aPollution monitoring series ;$v<3 >-5