M/S're. First a curious pseudonym for such a question. Hm?? Contingency is a buffer a margin to allow for error, unexpected events, change of plan etc. If you are designing something you always build in an extra factor for 'allowances'. It needs 3g for everyday use so you add 25% for exceedance margins. No-one likes to be operating on the edge all the time, so a little extra legal full is always welcome.