Survey report error in measured floor space

I had the surveyors in recently in preparation for getting my flat up on the market.

They measured 55sqm which is 6sqm less than when I purchased the flat. I queried this and they were adamant the previous surveyors were incorrect, so I had the previous surveyors in to confirm that the floor space was indeed 61sqm.

The recent surveyors agreed they would come back to do a double check - lo and behold, 61sqm. They apologised and quickly updated the single survey report.

The issue here is the valuation stayed the same at 61sqm as it did 55sqm - not a single difference. Is this possible? Does more than a 10% increase in measured floor space have 0 effect on the value of the property?