getPurchase returns the first subscription not the last one

Question

I am using the subscription model in Android. when I query inventory,the listener is as follows

IabHelper.QueryInventoryFinishedListener mGotInventoryListener = new IabHelper.QueryInventoryFinishedListener() {
        public void onQueryInventoryFinished(IabResult result, Inventory inventory) {
            Log.d(TAG, "Query inventory finished.");
            if (result.isFailure()) {
                mAct.alert("Failed to query inventory: " + result, true);
                return;
            }

            Log.d(TAG, "Query inventory was successful.");

            // Do we have the premium upgrade?
            Purchase premiumPurchase = inventory.getPurchase(SKU_PREMIUM);

Here the getPurchase returns the initial date of subscription, namely GPA.232423423423423.0

How can I get the purchase information of the latest subscription (Ie GPA.232423423423423.7)

I need to know the latest subscription date not the first

Thank you