Hi I have noticed that when key's value is double digit and has a fraction of 2, 

for example { "key": 13.2 } TJSON will output "key":  13.199999999999999

TJSON uses string_format(number, 0, 15) and then trims trailing zeroes to maintain original precision in case it matters.

Default string() function will round the number to two-digit precision.

Default number comparison operators use threshold as per math_set_epsilon.

In other words, the numbers are often stored with strange fractions, but the fact can be slightly obscured.