I just started tummy time. How long should bub last before she starts wailing and I put her back on her back?

My friend started out with just two to three minutes for her two-month old. She tries to have tummy time two to three times a day. Sometimes, she simply places her baby on top of her chest for a short while. Now her baby can last for a slightly longer period of time (around 10 mins) and is also showing more interest in trying to reach the things around her as she lift up her head to look around.