This appears to have its origin in the Planning Office due to references such as 53/17 - indicating the year (1953) and the sequential number (17).
The following significant matters are gleaned from this plan
53/17 was a proposal for a caravan site, refused. 50/151 shows the outline of the planned hotel on the corner of Welford Road and Teeton Road, presumably also refused. 49/146 the application for Sandhills. 57/78 the house on the south-east corner of the Welford Rd/Brixworth Rd junction.