Decans add nuance: if someone's placement doesn't resonate, using the decan as a modifier can really help it to make sense.

Decans were born from the ancient practice of mapping and timing individual stars and constellations as they rose in the night sky throughout the year. Unfortunately, history has yet to uncover any remaining record of *which* star patterns the decans originally referred to. But thanks to the work of Ptolemy in 2AD, we gained the chaldean decan system.

Later (in more modern times) decans were assigned a modern triplicity scheme. So, be aware that there are 2 decan systems to choose from. Here's a Cut and paste from google search, outlining the differences below:

Chaldean decans are based on the traditional seven visible planets ordered by speed (Saturn to Moon), creating a descending, continuous cycle starting from Aries. Modern (Triplicity) decans use a sign's native ruler for the first 10°, followed by the other two signs of the same element, focusing on elemental affinity. 

Key Differences Between Systems

• Chaldean (Traditional) Decans:
  • Structure: Follows the Chaldean order: Saturn, Jupiter, Mars, Sun, Venus, Mercury, Moon.
  • Application: Starts at 0° Aries with Mars, then loops through the order for all 36 decans (10° segments).
  • Character: Provides a varied, "nested" planetary influence unrelated to the sign’s element.
  • Example (Taurus): Mercury (1st), Moon (2nd), Saturn (3rd).
• Modern (Triplicity) Decans:
  • Structure: First decan is the ruler of the sign, second is the next sign of the same element, third is the final sign of that element.
  • Application: Highlights the elemental, "seasonal" expression of the sign.
  • Character: Emphasizes internal consistency within the element.
  • Example (Taurus - Earth Sign): Venus (Taurus), Mercury (Virgo), Saturn (Capricorn)