What should I enter for exclusion percentage if my statement does not list one?

You don't need to enter an exclusion percentage.  Since the amount in Box 2c is zero, you can delete the Box 2c entry.  The exclusion percentage screen will only generate when there's an entry in Box 2c of your Form 1099-DIV.

To delete the zero entry from Box 2c of Form 1099-DIV in TurboTax Online:

1. Select Tax Home in the left pane
2. On the Hi, let's keep working on your taxes! screen, select the dropdown to the right of Income & Expenses
3. Select Work on other income or Pick up where you left off, as appropriate
4. Select Edit/Add to the right of Investments and Savings (1099-B, 1099-INT, 1099-DIV, 1099-K, Crypto)
5. Select Review next to the appropriate Dividends on 1099-DIV entry, or select the dropdown to the right of the appropriate Dividends (1099-DIV) entry and select Edit
6. On the  Let's get the info from your 1099-DIV screen, delete the $0 entry in Box 2c - Section 1202 gain, then select Continue