What is the maximum value an entry in a leaderboard using the Google Play Services can have?
The leaderboard documentation doesn't explicitly say (as of this writing).
However if you look at the documentation for the C++ API's
Score object, you can see that the value of the score is exposed as a
uint64_t, which means you have 64 bits of storage for your scores (as integers, times, or currencies).
As an integer this value is 18,446,744,073,709,551,615.
Note that you can also set explicit upper and lower limits on scores allowed on the leaderboard via the API.