Thanks for your bug report. This conversion is handled by the basic atof() CRT call which converts text to a float and is used throughout mIRC. On the atof() page, Microsoft says that support for 'd' and 'D' is non-standard and it looks like it was removed in later versions of the CRT. mIRC is currently compiled with Visual C++ 2008. I could probably add support for 'd' and 'D' to MAPM to make it work in the same way as non-bigfloat.