How to set Proration mode while updating Subscription With Google play console

[Veclar]

i am using an in app bliling subscription method in my app. i am using getBuyIntentToReplaceSkus to update my subscription.
buyIntentBundle = mService.getBuyIntentToReplaceSkus(5,
mContext.getPackageName(),oldSkus, sku, itemType, extraData);

i want to add proration mode while updating my sku. I have seen a method here on delevoper forum https://developer.android.com/google/play/billing/billing_subscriptions#Allow-upgrade But i don't know how use this with getBuyIntentToReplaceSkus. Here is the code that i have seen on that link.

BillingFlowParams flowParams = BillingFlowParams.newBuilder()
.setSku(skuId)
.setType(billingType)
.setOldSku(oldSku)
.setReplaceSkusProrationMode(replaceSkusProrationMode)
.build()
int responseCode = mBillingClient.launchBillingFlow(activity, flowParams);

 

[Veclar]

I also need to know what happens to the remaining days of previous subscription when you upgrade or downgrade your subscription.