A balance returned by Fireblocks API has a maximum of 17 decimal digits (number of digits left of the decimal point + number of digits right of the decimal point). Balances with more than 17 decimal digits will be rounded to the nearest digit at the last digit.
If you want to use the balance returned by Fireblocks API as an input argument for your next transaction to sweep the entire balance of a vault account to another destination, consider rounding down the 17th digit. Otherwise, your transaction might fail with an error of insufficient balance or insufficient funds for a fee.
Example 1: 1.5999842313164864354987949849431321688978979794564564656119818916866846484686484613534846
Note: The number above has more than 17 decimals and will be returned as this string: 1.5999842313164865
Example 2: 125232362323663422632351313251.599984231316486435498794984943132168897897979456456465
Note: Fireblocks supports 16 decimals and will returned the number above as this string: 1.252323623236634e+30