HPLC or UPLC can describe a chromatographic purity profile. A reported peak area percentage should not be interpreted as the mass fraction or content of the target peptide without an appropriate quantitative method.
When comparing results, ask for the sample identity, method, chromatogram, reporting basis, reference material and any known related substances. A separate assay may be needed to answer how much target material is present.
Analytical procedures should be suitable for the question they are intended to answer. See the ICH Q2(R2) guideline.