On Maths Pathway reports, teachers can choose to include students' level data. Unless otherwise indicated, these levels correspond to the Australian Curriculum. To help understand these levels, if a student is learning 'at level' in grade 7 for example, the curriculum expects them to achieve a level 7.0 by the end of the year to achieve a passing grade.
Below is a level bar displaying a student's current data, which is similar to what you might see if your student's school decides to report levels. The solid bar indicates the areas that the system is sure about: content that has been mastered either on the diagnostic or through normal testing. In this case the student has mastered up to (at least) level 4.8.
The error bars are used to indicate areas where the system hasn't had a chance to test yet. Once a student has been fully diagnosed (by doing all four parts of the diagnostic), there shouldn't be any error bars. Where the error bar starts is the "worst case assumption" about a student's level. Conversely, the end of the error bar is the "best case assumption".