Multiple and/or approximate playing times:

If more than one playing time is recorded in a note, each is coded in a separate subfield $a. If more than six playing times are recorded in a note, field 306 is generally not used.

If the abbreviation ca. precedes an approximate playing time, this abbreviation is disregarded when recording field 306.

Example:

500 ##$aDurations: 13:56 ; ca. 20:05.

306 ##$a001356$a002005