[#ymmvabbr]: YMMV
Abbreviation for “Your mileage may vary”.
[#ymmv]: “Your mileage may vary” (“YMMV”)

Likely referring to America where miles (rather than kilometers) are typically used as a reference, the connotation is that results may vary. A person should expect that success achieved in one instance might not be repeated in another instance. Differences, such as different hardware being used, may be quite likely to result in different results. Even a person who has success with a computer may find that the success is not repeated at a later time.