For distribution of a pooled library, depositing labs provide aliquots to Addgene, and we do not perform any additional amplification steps. Therefore, the DNA you receive from us is what is described by the depositing lab. Depositors provide information on the pooled library page, or in the associated publication, describing how they have ensured full coverage for a particular library.
For example, according to the associated publication, the Sabatini lab ensured full coverage as follows: "To preserve the diversity of the library, at least 20-fold coverage of each pool was recovered in each transformation and grown in liquid culture for 16-18 hours.” Similarly, the Zhang lab ensured full coverage as follows: "To ensure no loss of representation, 36 parallel transformations were performed using the same ligation reaction and plated onto 245 mm x 245 mm plates with carbenicillin selection (50 ug/ml), which yielded 166 X library coverage".