How to use the jsbi.toNumber function in jsbi

SetPosition(trackId, position) {
    let e = {
      trackId: trackId,
      // XXX overflow
      position: JSBI.toNumber(position)
    };
    this.player.emit('position', e);
  }

Seek(offset) {
    // XXX overflow
    offset = JSBI.toNumber(offset);
    this.player.emit('seek', offset);
  }

JSBI.equal(a, b);
JSBI.notEqual(a, b);
JSBI.lessThan(a, b);
JSBI.lessThanOrEqual(a, b);
JSBI.greaterThan(a, b);
JSBI.greaterThanOrEqual(a, b);

JSBI.EQ(a, b);
JSBI.NE(a, b);
JSBI.LT(a, b);
JSBI.LE(a, b);
JSBI.GT(a, b);
JSBI.GE(a, b);

a.toString();
JSBI.toNumber(a);
a instanceof JSBI;

JSBI.asIntN(64, JSBI.BigInt('42'));
JSBI.asUintN(64, JSBI.BigInt('42'));

public static clampToSafeIntegerRange(value: JSBI): number {
        if (JSBI.greaterThan(value, this.NUMBER_MAX_SAFE_INTEGER)) {
            return Number.MAX_SAFE_INTEGER;
        }
        if (JSBI.lessThan(value, this.NUMBER_MIN_SAFE_INTEGER)) {
            return Number.MIN_SAFE_INTEGER;
        }
        return JSBI.toNumber(value);
    }