What does 95 and 99% confidence factor mean in relation to the strength of the composite?

The 95 and 99% confidence levels are a means to determine probability of the composite strength being what is stated or claimed.  This value is used in the qualification testing as a means to narrow down the product's actual strength.  Literally, this means that by using the 99% confidence level of the composite strength, you can be 99% confident that the strength stated will be the minimum of what is actually found in the field.  The higher this is, typically, the lower the strength value used as this relates to 2 or 3 standard deviations from the average tested values.