No.

In Jain tapasya counting:

• Chhath means 2 upvas continuously.
• Attham means 3 upvas continuously.

So if someone says Chhath + Attham, then together it is:

2 + 3 = 5 upvas

But individually:

• Chhath is not 5 upvas
• Attham is not 5 upvas
• Chhath Attham together can mean total 5 upvas