The adjective endings after “der”-words are all weak, meaning that they do not indicate gender of the nouns they modify in and of themselves. In fact, these particular adjective endings are either ‘e’ or ‘en.’
Here is a simpler table with the adjective endings after the definite article:
HINT: All adjective endings after all der- or ein-Words (der, die, das, dem, dieses, jeder, ein, keine, manche, solcher, etc.) in the dative and genitive cases are always ‘en.’ This means that you only have to memorize the changes between the definite and indefinite articles tables, specifically the masculine and neuter in the nominative (+er, +es after the indefinite article), and the neuter in the accusative (+es; the feminine in both nominative and accusative in either table is exactly the same: ‘e’).