I imported the swiid_summary.csv file, and the data for some countries seem to be given in different units; for example, in one country, gini_disp is 313 and gini_mkt is 33. How can I interpret these data?

The issue here is that the swiid_summary.csv file is saved using RFC 4180 csv conventions, that is, with a dot marking the decimal and a comma separating values. If you are in a locale that observes different conventions—many countries use commas to indicate the decimal and semicolons to separate values—your software’s default settings may not read the data correctly. Be sure to specify the decimal marker and value delimiter appropriately when loading the file: all SWIID values are Gini indices and so fall between zero and one hundred.