Transcription errors exist in various publications of James Craig's baptismal record. See notes below.
The typed transcription shown at Ancestry.com shows the following:
1 Feb 1744/45 Robert McMachan, a chlid baptized named Martha. I believe this to be a straightforward transcription error.
A work taken from the appendix of an unknown book, which is entitled "BAPTISMAL RECORD OF THE REV. JOHN CRAIG, D.D., OF AUGUSTA COUNTY, VIRGINIA, 1740-1749, CONTAINING ONE THOUSAND FOUR HUNDRED AND SEVENTY-NINE NAMES, (First publication of the original record)shows the following entry:
McMachaie, Robt. ---Thomas Feb 1 1745 Significant difference in the spelling of the father's name.