This is the 228th most frequent Spanish word.
seis
The number six.
Here, 'seis' is used as a numeral adjective modifying the noun 'manzanas' to specify the quantity.
Compré seis manzanas en el mercado.
I bought six apples at the market.
In this sentence, 'seis' functions as part of the expression indicating time.
El reloj muestra que son las seis.
The clock shows it's six o'clock.
The word 'seis' in this context is a numeral that specifies the duration of the activity in hours.