The SV1 is referring to the service line, and more specifically, SV1-02 is referring to the charge amount. Therefore, the rejection message is indicating that they do not like the charge amount. Specifically, because they are complaining about leading zeros, they are probably referring to a charge amount of less than 1.00.
How to fix
The charge amount is entered in Therabill on the add / edit session form. If you are on the EDI error page in Therabill, then you can open up the edit session form for the session on the claim by clicking the date(s) of service on the right hand side of the error page, under the section Edit Claim Information. On the edit session form, change the charge amount to an amount greater than 1.00.
But these are Functional Limitation Codes, and the dollar amount is automatically set to 1 penny.
According to Medicare rules, the charge amount for Functional Limitation Reporting (FLR) G-codes should be set to a nominal amount of 1 cent. If you are receiving this error back for an FLR code charge amount, then it may that some other error on the claim set off this error (that is, they are reporting back an incorrect error message that was caused by a different (but un-reported) error on your claim. You may need to call the payer's EDI department to find out exactly why they are rejecting your claim.