On a series of dives using using mixtures the residual nitrogen category for a repetitive dive should be determined from Table 2 and applied in table 3 of the mixture that you intend to use for the next dive.
For the initial dive it is recommended to use the mixture with the lowest oxygen (e.g. air) and for repetitive dives use a mixture with more oxygen.
Residual nitrogen time (RNT)
The time required for nitrogen to escape from body tissues depends on the depth and duration of the dive. Residual nitrogen time indicates the residual nitrogen in the body after a dive and the time spent at the surface. The residual nitrogen time is expressed in minutes of “penalty” time, scaled to the corresponding depths.
In the left column, find the line with the letter value of of the residual nitrogen category before a second dive.
In the upper row, find the column with the value of the planned re-dive depth. If the planned depth is missing, you should take the closest value. (This will add a little “penalty” time, increasing your safety).
At their intersection you will find the value of remaining nitrogen time for the selected depth.