You should not increase your PCR cycle for low input (<5 ng) DNA samples. We have specifically designed this kit to work with low-input samples, and we typically find that the recommended cycle number (14) is sufficient regardless of input amount. If you are struggling with low yield after library prep using the recommended number of cycles, we recommend troubleshooting your CUT&RUN workflow and/or troubleshooting your library prep workflow before considering an increase in cycle number.
If you do choose to increase the cycle number, keep in mind that doing so will likely lead to increased PCR duplicates, off-target fragments, and poorer sequencing quality due to increased background noise.