Message type: E = Error
Message class:  CNV_20100 - Messageclass for chart of account conversion 
Message number: 257
Message text: In T8G17 for new CoA &1: Lower limit &2 is greater than higher limit &3
Since SAP believes that this specific error message is 'self-explanatory,' no more information has been given.The majority of messages in the SAP system have a message text, however this is frequently insufficient to comprehend or resolve the problem.
To make things easier, more detailed information is frequently added to describe the issue, how to fix it, and the necessary steps or configuration modifications.
Unfortunately, there isn't any extra information in this error notice.
First, use our AnswerBot below to get a possible cause and solution (requires a premium subscription).
Also, review the in-depth Common Questions & Answers listed below; you could discover a solution there or be able to connect with others who have faced similar challenges.
You can also try searching the SAP support portal (support.sap.com) but you need a special user ID to access it. It is possible that an SAP support note exists that provides additional details about the mistake or even steps for fixing it.
The SAP error message CNV_20100257 typically occurs during the conversion process in the context of a new Chart of Accounts (CoA) setup. This specific error indicates that there is a configuration issue where the lower limit of a range is greater than the higher limit, which is logically incorrect.
Cause: The error message CNV_20100257 in T8G17 arises due to the following reasons: Incorrect Configuration: The lower limit for a certain account or range has been set higher than the upper limit. This can happen during the mapping of accounts or while defining ranges for account groups. Data Migration Issues: If you are migrating data from one CoA to another, there may be inconsistencies in the data that lead to this error. Manual Entry Errors: During the setup or configuration of the new CoA, manual entry errors can lead to incorrect limit settings.
Solution: To resolve this error, you can follow these steps: Check Configuration: Go to the transaction code
 Get instant SAP help. Sign up for our Free Essentials Plan.
Get instant SAP help. Sign up for our Free Essentials Plan. 
CNV_20100256 &1 and &2 have different cost centers in controlling area &3
 adjust the mapping of the cost elements accordingly. Check if you really want the merge to take place in this way. If not,How to fix this error?  War...
CNV_20100255 &1 is blocked for posting in company code &3, whereas account &2 is not
What causes this issue?  Account &V1& is blocked for posting in company code &V3&, whereas account &V2& is <ZH>not</&...
CNV_20100258 In T8G17 for new CoA &1: Overlap of intervals: &2; &3
Self-Explanatory Message Since SAP believes that this specific error message is 'self-explanatory,' no more information has been given.The majority of...
CNV_20100259 Item category changes in CoA &1 (SAKNR,LINETYPE): &2 => &3
What causes this issue?  According to the mapping, the item category of a G/L account (table T8G17, field LINETYPE) changes. However this is not allow...
Click on this link to search all SAP messages.