C# FileStream, file is larger than last Position -

i'm attempting write filestream. after last write, see stream.position 11,247,160. after check, there is flush, close, , using automatically disposes of filestream. value of position when hits line containing close call. however, when @ file in explorer, size 12,847,148 bytes, or 1.5mb larger. when read data, there's bunch of gibberish data @ end. has seen before?

thank you.