SNPs which are found in more than one haplogroup used to be given names ending in a or b. More recent papers show these SNPs ending in .1 or .2. Earlier versions of the ISOGG tree show both names, but the current tree shows only the more recent notation.
Example:
      Current: 12f2.1    Former: 12f2a
      Current: 12f2.2    Former: 12f2b

SNPs that appear in a single haplogroup with multiple y-positions are now shown with extensions of _1, _2.
Example:
      P7_1, P7_2, P7_3.