Currently capped at 120. Makes sense IRL, but for some VATSIM events (e.g. Santa) it may be useful to carry up to, say, 240 minutes-- currently we have to either estimate the extra fuel required in terms of weight, or also include more contingency and/or final reserve.
An increase to the current cap would be convenient.
This will be possible in the new SimBrief version, currently in development. The extra fuel box will be a free-text field and no longer limited to the options in the drop-down.