The grammar method seeks to apply and teach Hebrew grammar. One goal of grammar is to present the various rules of plural-singular. Lv14-12 states And the priest shall take one male lamb, and bring it near for a guilt offering, with the pint [literally log] of oil, and wave them for a wave offering before the Lord.

Rashi commenting on the Biblical phrase and wave them states [Them refers to]
• the lamb and
• pint of oil.

Rashi is terse and enigmatic. To fully understand Rashi we must read the full Sifrah which he cites. We in fact cite the Sifrah using the simple grammatical explanation offered by the great 19th century commentator Malbim: Note the contrasts of
• the singular it, and bring it near
• the plural them, and wave them
• the singular wave offering, for a waive offering.
Proper grammar, as taught say in high school and introductory college courses would require, for purposes of clarify, a consistent use of singular and plural. The verse should read as follows: And the priest shall take one male lamb with the pint of oil and bring them near for a guilt offering and wave them for a wave offerings before the Lord.

Rashi therefore can make inferences from the alternate uses of singular and plural
• The singular wave offering vs plural wave offerings shows that there is one waive offering
• the plural them, shows that this singular wave offering is done to both objects, the lamb and oil-pint So we do not waive the oil separately and the lamb separately as we would then have two wave offerings.
• the singular bring it near shows that a separate treatment for the lamb and oil-pint is possible. If you inadvertently waived only one of the two objects (oil,lamb) then bring it near (either the oil or lamb whichever was forgotten) and waive it separately.