Solution
The digital pattern labels are stored on the NI-Digital module's onboard FPGA's memory. This memory is a tiered memory structure enables low latency branching and large storage with different tiers: Fast Vector Memory (FVM), Cache Vector Memory (CVM), Large Vector Memory (LVM).
Because the vectors and the labels both use FVM (Fast Vector Memory), both amounts must be considered for determining number of labels possible. As rule of thumb, the max number of labels is between 600 and 1500.
More specifically: FVM has a max of 6144 vectors, each label forces the vector it is on plus the next 3 vectors (total of 4) into memory. Because the vectors and the labels both use FVM (Fast Vector Memory), a user can use about 600 labels if all labels are followed by 160 vectors or they can use about 1500 labels if all labels are followed by 4 vectors. From (Vector Memory - NI), to help to deal with running out of memory , 'If you run out of FVM and CVM, reduce the number of vector labels and call opcodes in the pattern. Alternatively, combine patterns, such as using source or capture functionality to eliminate the need for unique patterns for each DUT register access.'