Choose 'Any' when the string offset can be located at any position in the file. 

Choose '≤' when the string offset is at the offset specified or before the offset. The string offset is typed in the field on the right. 

Choose '≥' when the string offset is at the offset specified or after the offset. The string offset is typed in the field on the right.

Choose '=' when the string offset is at a particular location in the viral resource. The string offset is typed in the field on the right.