User Assertion Failed !
This message occurs if the execution of a macro reaches a point where the Assert function is called with its parameter bCondition false and its bAbortScript parameter true. This is not an application error; it is an error generated because the person who wrote the macro decided that if certain conditions were not true, then an error should be generated.
The second line contains the text of the sMessage parameter of the Assert function and usually describes what condition was not true. The third line gives you detailed information about the context in which the error was generated : the page number, the date of the token, the token being evaluated, and the origin of that token.
The origin of the token may be different than the token itself, if tokens are used recursively. In the example above, the current token is [a4*5d], but one sees that actually this token came from the evaluation of the [4*1*5d] token. The origin is the exact text that is in your GridTemplate.