Answer:
The "Divide Line → Distance" option has the fixed minimum limit of 0.50 mm. If you want to shorten the line (for example, 0.25 mm), divide it to 1.00 mm first. Then, you can use the "Divide Line → n Intermediate Nodes" function to generate three intermediate nodes. Thus, you will get the line length of 0.25 mm.
Important!
One of each file unites adjacent nodes that are closer together than 0.5 mm. In the case mentioned above, this has to be adjusted by means of the "Tools → Regenerate Model" feature (see Image 02).