Cite the scanned version of the original dicionary like this:
Toller, T. Northcote, and Joseph Bosworth. "ofer-tæl." An Anglo-Saxon Dictionary: Based on the Manuscript Collections of the Late Joseph Bosworth : Supplement. Oxford: Clarendon Press, 1921. 661.
, es; n. An odd number :-- Ðæra pipercorna sý ofertæl, ðæt ys ðý forman dæge án and þrittig, and ðý óðrum dæge seofontýne, and dý þriddan dæge þreótýne, Lchdm. i. 288, 8.