Dancers count by steps rather than by measures, and salsa typically features eight steps per phrase (two measures of 4/4 time). See this similar question on Quora for details: [In] each 4/4 measure, a dancer steps three times, either left/right/left or right/left/right.
How is salsa counted?
Salsa music is counted in 8 beat phrases. These 8 beats constitute two "musical measures" of 4 beats each.
Why do you count to 8 in dance?
In music there are typically 4 counts, or beats, per measure. In dance, a measure is usually “musically paired” with a second measure. These two measures equal a total of 8 counts, which is why dancers count in sets of 8. 8 counts keep track of the beat and tempo, but break up the song into manageable sections.
What is the time signature for salsa?
With salsa dancing, you will use two measures of the music for a cycle in the basic steps. Traditionally salsa uses a 4/4 time signature. It's often played in groups of eight beats.