The main difference is that manga volumes usually collect several single chapters together. Volumes often have a coherent theme or story arc within them.
The latest version of Douluo Continent manga was 22 volumes. However, due to copyright issues, the latest version might not be available on domestic manga platforms. If you need to understand the contents of the 23 volumes of Douluo Continent comics, you are recommended to go to the relevant comics platform or purchase the original comics to read.
Seraph of the End manga has a total of approximately X volumes. The series has been ongoing, and the number keeps increasing with new releases and story arcs.
Well, as of now, Vagabond manga has approximately 37 volumes. But keep in mind that this number might change if new volumes are released in the future.