what does this mean in 'computeSVD()' python

Question

my question is what does the number 5 refer to in this computeSVD(5, computeU=True):

from pyspark.mllib.linalg import Vectors
from pyspark.mllib.linalg.distributed import RowMatrix

rows = sc.parallelize([
    Vectors.sparse(5, {1: 1.0, 3: 7.0}),
    Vectors.dense(2.0, 0.0, 3.0, 4.0, 5.0),
    Vectors.dense(4.0, 0.0, 0.0, 6.0, 7.0)
])

mat = RowMatrix(rows)

svd = mat.computeSVD(5, computeU=True)  <--- the 5 here 
U = svd.U       # The U factor is a RowMatrix.
s = svd.s       # The singular values are stored in a local dense vector.
V = svd.V       # The V factor is a local dense matrix.

i found this code in this link : https://spark.apache.org/docs/2.2.0/mllib-dimensionality-reduction.html