This retains every line with a numeric character somewhere in it and discards the rest.
What digits usually mark
Model numbers, years, sizes, quantities, versions, prices. In a keyword list, a digit frequently signals a more specific and more commercial search than the same phrase without one.
Isolating specific intent
Filtering to numeric terms extracts the part of a keyword set where searchers already know what they want — a size, a model, a year. Those terms convert differently from general research queries.
The complement
Removing lines with digits gives the other half. Both halves are useful; they simply support different content.
Try it: Keep Lines With Digits on SeoWolf's Notepad.