Difference in £matched on website and API?

[cwfmoore]

I have noticed a significant difference between the website volume matched and the returns I am getting from API requests.

I have checked I am using the non-delayed key. I have compared timestamps to make sure also. I have a screen shot.

I thought perhaps a non runner may be included in the website data, but it is consistent on every market, perhaps 20% behind. Very puzzled.

The API amount is in the bottom left, red circles provided.

https://imgur.com/a/79726Cq