Then calculate the elevation of the SET table relative to MTL in "half-tide units." As a reminder, half-tide units are "elevation-in-meters / (0.5 * GTU-in-meters )"
Then, plot these data on a graph so you can understand the relationship between SET elevation and measured elevation changes.
A line using the accretion spreadsheet data can then be fit through the data to the best of your capability.
e.g. Fig 4 from https://www.sciencedirect.com/science/article/pii/S1364815216302705#fig4
Often SET tables are not set at elevations throughout the tidal range and are focused up around MHW so you would need to estimate the other portions of the range or use a model such as MEM3 to help fill out the relationship between marsh platform elevation and predicted accretion rates.
This is a quick birds-eye view of the procedure, please ask specific questions about the spreadsheet and we will answer them ASAP.
Love the user name BTW.
Regards! - -Jonathan