Hola, Wanda.
At about es "alrededor", you can also say "aproximadamente" or "cerca de" both would mean "close to".
Now, you can also use these expressions not only for time.
I have about three or four books on that subject at home.
Tengo alrededor de tres o cuatro libros sobre ese tema en casa.
I saw about 40 persons.
Vi alrededor de 40 personas.
Vi unas 40 personas. (literally "some").
She is about 1.70.
Ella mide alrededor de 1.70.
I hope this is helpful.