Apparently when it's the number of homes allowed on a piece of land by Wrexham Council.
Wrexham Council's own Unitary Development Plan, which still guides planning in this borough, states that "no more than 160" homes are allowed on the piece of National Trust land at Rhostyllen.
Tonight's planning committee debate on the matter, at which Cllr Carrie Harper and myself were not allowed to contribute or vote, heard planning officers argue that 160 was not a fixed number but could - in fact - mean 223. This, by coincidence, is the number of homes the National Trust now wants to build on the farmland. The willingness to accommodate developers was a symptom of the old regime at Wrexham Council and tonight was a reminder that that old regime still has some life in it.
And what of those rapacious developers?
The National Trust, whose very name now seems like a sick joke, has decided that it can only win the argument by misleading the public. At a recent meeting with campaigners they stated that no National Trust money could be used to subsidise Erddig because it was a special case. We reported this honestly to the press. The Trust then claimed that this was not the case because it had spent £1m from its central funds on Erddig in the past five years.
Tonight we received a clarification of this doublespeak - it appears the Trust has merely loaned the money to Erddig and, when the development takes place, it will have to repay that loan in full.
Don't trust the trust.