Question about a dimension in this IC package drawing
You can read more about those symbols in this Drafting Manual but those particular symbols are related to the tolerance rather than size:



It seems to me the seven pins have a diameter of 0.6 mm +/- 0.1mm with a spacing of 1.27 mm between them. It's quite common for dimensions to be prefixed by "7 x" etc to indicate the same dimension applies to multiple items.