4 If only one is sounded, the leaders—the heads of the clans of Israel—are to assemble before you.

Read Numbers 10:4 Using Other Translations

And if they blow but with one trumpet, then the princes, which are heads of the thousands of Israel, shall gather themselves unto thee.
But if they blow only one, then the chiefs, the heads of the tribes of Israel, shall gather themselves to you.
But if only one trumpet is blown, then only the leaders—the heads of the clans of Israel—must present themselves to you.