When looking at assignment possibilities in the Assignment Panel there are a variety of useful options available. Intra-residue is a useful option for spectra recorded with short mixing times where you would on the whole only expect to see intra-residue cross-peaks. Double Tolerances allows you temporarily to double the tolerances set for that spectrum. In this way you can have a slightly lower value as your standard and not be swamped with assignment possibilities all the time. But when there is a peak which is slightly out for some reason you can still find the correct assignment option and make the assignment. Correlated Dims uses the Experiment Type selected previously to reduce your assignment options. For example, in an NCACX experiment the N and Cα must always belong to the same residue. The is encoded in the Experiment Type and so when you select Correlated Dims for an NCACX the assignment possibilities will be reduced to those where the N and Cα belong the same residue (unless there are no such pairs within the tolerances used). The CX dimension will not be affected since this is a through-space transfer and could go to any residue. Only if you select the Intra-residue option as well, will you only be given fully intra-residue assignment options. By selecting a Labelling Scheme you can filter the assignment possibilities based on the way in which your molecule is labelled. See here for more details.