When used in a charter party contract, abt - about, means that  a margin of 5% more or less would apply to quantity of cargo, bunkers or speed.

If it is used in connection with a period of time about refers to usually 15 days, although each case should be considered on its own merit.

Example Usage: Below examples are collected from well-known standard format time charter party contracts under field description of vessel's "Speed Capability in Knots and Fuel Consumption".

NYPE 1946 lines 9 –10
“... and capable of steaming, fully laden, under good weather conditions about ... knots on a consumption of about ... tons of … best grade fuel oil ...”

NYPE 1993 lines 18-20
... Speed about ... knots, fully laden, in good weather conditions up to and including maximum Force... on the Beaufort wind scale, on a consumption of about ... tons of ...


PART I Box 12

Speed capability in knots (abt.) on a consumption in tons (abt.) of m …

PART II lines 10-13

... and fully loaded capable of steaming about the number of knots indicated in Box 12 in good weather and smooth water on a consumption of about the number of tons fuel oil stated in Box 12 ...