Promotion number of redemptions

Hi,

I'm looking for a way to fetch the current number of redeemed elements for a promotion, similarily to what is displayed when listing the different Campaigns in the admin-panel as displayed here (the Redemptions column) :

I have tried with 

var redemptionImitator = ServiceLocator.Current.GetInstance<IRedemptionLimitService>();
var limitNumber = redemptionImitator.GetRemainingRedemptions(new List<PromotionData>() { PromotionDataElement }, cart.CustomerId, cart.GetFirstForm().OrderFormId);

but with no luck. The afformentioned approach always returns a { Count: 1 }.

Any help is greatly appreciated.