Performing a library concentration measurement is not required or recommended, even when combining with other NGS libraries that are of a differing end concentrations.

There is no library clean-up step in digitalMLPA, meaning that the library contains a mixture of full amplicons, sample DNA, carrier DNA, and non-ligated probes. Except for the amplicons, these will not contribute to the sequencing products but do contribute to the measured DNA concentration. You should not adjust the recommended final concentration of the digitalMLPA library to match that of other NGS libraries.